Method and system for ensuring reception of a communications signal

ABSTRACT

The present invention includes a system and method for ensuring reception of a communications signal. A modulating baseband signal with desired information is accepted, and a plurality of redundant spectrums is generated. Each redundant spectrum comprises the necessary amplitude, phase, and frequency information to substantially reconstruct the modulating baseband signal. It is expected but not required that the redundant spectrums will be generated at a first location and sent to a second location over a communications medium. At the second location, the redundant spectrums are independently processed to recover a demodulating baseband signal for each of the redundant spectrums. In one embodiment, an error detection process is employed at the second location to detect and eliminate those demodulated baseband signals that have been corrupted during transmission. An error-free demodulated baseband signal is selected from the remaining demodulated baseband signals. The error-free demodulated baseband signal is representative of the modulating baseband signal sent over the communications medium.

CROSS-REFERENCE TO OTHER APPLICATIONS

The following applications of common assignee are related to the presentapplication, have the same filing date as the present application, andare herein incorporated by reference in their entireties:

“Method and System for Down-Converting Electromagnetic Signals,” Ser.No. filed Oct. 21, 1998, now U.S. Pat. No. 6,061,551, issued May 9,2000;

“Method and System for Frequency Up-Conversion,” Ser. No. 09/176,154filed Oct. 21, 1998;

“Integrated Frequency Translation and Selectivity,” Ser. No. 09/175,966filed Oct. 21, 1998, now U.S. Pat. No. 6,049,706, issued Apr. 11, 2000;and

“Universal Frequency Translation, and Applications of Same,” Ser. No.09/176,027 filed Oct. 21, 1998, now Abandoned;

BACKGROUND OF THE INVENTION

I. Field of the Invention

This is a continuation of pending application Ser. No. 09/176,415, filedOct. 21, 1999

The present invention relates generally to electromagneticcommunications, and more particularly, to a method and system forensuring reception of a communications signal.

II. Description of the Related Art

Communication links utilize electromagnetic signals (EM), in the form ofelectromagnetic waves, to carry analog or digital electronic informationfrom a first location to a second location. In doing so, a basebandsignal, containing the information to be transmitted, is impressed on anoscillating signal to produce a modulated signal at the first location.The modulated signal is sent over the communications link to the secondlocation. At the second location, the modulated signal is typicallydown-converted to a lower frequency, where the baseband signal can berecovered.

All EM signals can be sufficiently described in both the time domain andthe frequency domain. FIG. 1A depicts a baseband signal 102 in the timedomain that starts at time to and ends at a time t₁. The baseband signal102 can represent any number of real world occurrences. For example,baseband signal 102 could be the voltage output of a microphone for agiven acoustical input. FIG. 1B illustrates spectrum 104, which is thefrequency domain representation of baseband signal 102. Spectrum 104depicts the relative amplitude of the sinusoidal components that whensummed together with the correct relative phase will construct basebandsignal 102 in the time domain. In other words, the spectrum 104represents the relative amplitude and phase of the sine waves thatconstitute baseband signal 102 in the time domain.

Theoretically, a time-limited baseband signal (like baseband signal 102)has an infinite number of sinusoidal frequency components. That is, the“tail” of spectrum 104 will continue to infinity. However, the amplitudeof the sinusoidal components in spectrum 104 decrease with increasingfrequency. At some point, the higher frequency components can be ignoredand filtered out. The highest frequency remaining defines the “frequencybandwidth” (B) of the spectrum 104. For example, if spectrum 104corresponded to a human voice signal, the bandwidth (B) would beapproximately 3.5 KHz. In other words, those sine waves beyond 3.5 KHzcan be filtered out without noticeably affecting the quality of thereconstructed voice signal.

The signal with the simplest frequency domain representation is that ofa single sine wave (or tone) at a given frequency f₀. Sine wave 106having a frequency f₀, and its spectrum 108 are shown in FIGS. 1C, and1D, respectively. Sinusoidal signals are one type of periodic signals(or repeating signals) that may also be referred to as “oscillatingsignals”.

Amplitude modulation, a common modulation scheme, will be explored belowto illustrate the effects of modulation. FIGS. 1E and 1F illustratemodulated (mod) signal 110 and its corresponding modulated spectrum 112.Modulated signal 110 is the result of amplitude modulating sine wave 106with baseband signal 102. In the time domain, the amplitude of modulatedsignal 110 tracks the amplitude of the baseband signal 102, butmaintains the frequency of sine wave 106. As such, sine wave 106 isoften called the “carrier signal” for baseband signal 102, and itsfrequency is often called the “carrier frequency.” In this application,information signals that are used to modulate a carrier signal may bereferred to as “modulating baseband signals”.

In the frequency domain, amplitude modulation causes spectrum 104 to be“up-converted” from “baseband” to the carrier frequency f₀, and mirrorimaged about the carrier frequency f₀, resulting in modulated spectrum112 (FIG. 1F). An effect of the mirror image is that it doubles thebandwidth of modulated spectrum 112 to 2B, when compared to that ofmodulated spectrum 104.

Modulated spectrum 112 (in FIG. 1F) is depicted as having substantiallythe same shape as that of modulated spectrum 104 (when the mirror imageis considered). This is the case in this example for AM modulation, butin other specific types of modulations this may or may not be so as isknown by those skilled in the art(s).

Modulated spectrum 112 is the frequency domain representation of what issent over a wireless communications link during transmission from afirst location to a second location when AM modulation is used. At thesecond location, the modulated spectrum 112 is down-converted back to“baseband” where the baseband signal 102 is reconstructed from thebaseband spectrum 104. But in order to do so, the modulated spectrum 112must arrive at the second location substantially unchanged.

During transmission over the wireless link, modulated spectrum 112 issusceptible to interference. This can occur because the receiver at thesecond location must be designed to accept and process signals in therange of (f₀−B) to (f₀+B). The receiver antenna accepts all signalswithin the stated frequency band regardless of their origin. As seen inFIG. 1G, if a second transmitter is transmitting a jamming signal 114within the band of (f₀−B) to (f₀+B), the receiver will process thejamming signal 114 along with the intended modulated spectrum 112. (Inthis application a jamming signal is any unwanted signal regardless oforigin that coexists in a band occupied by an intended modulatedspectrum. The jamming signal need not be intended to jam.) If the powerof jamming signal 114 is sufficiently large, then modulated spectrum 112will be corrupted during receiver processing, and the intendedinformation signal 102 will not be properly recovered.

Jamming margin defines the susceptibility that a modulated spectrum hasto a jamming signal. Jamming margin is a measurement of the maximumjamming signal amplitude that a receiver can tolerate and still be ableto reconstruct the intended baseband signal. For example, if a receivercan recover info signal 102 from spectrum 112 with a maximum jammingsignal 114 that is 10 dB below the modulated spectrum 112, then thejamming margin is said to be −10 dBc (or dB from the carrier).

Jamming margin is heavily dependent on the type of modulation used. Forexample, amplitude modulation can have a typical jamming margin ofapproximately −6 dBc. Frequency modulation (FM) can have a jammingmargin of approximately −3 dBc, and thus more resistant to jammingsignals than AM because more powerful jamming signals can be tolerated.

The Federal Communications Commission (FCC) has set aside the band from902 MHZ to 928 MHZ as an open frequency band for consumer products. Thisallows anyone to transmit signals within the 902-928 MHZ band forconsumer applications without obtaining an operating licence, as long asthe transmitted signal power is below a specified limit. Exemplaryconsumer applications would be wireless computer devices, cordlesstelephones, RF control devices (e.g. garage door openers), etc. As such,there is a potentially unlimited number of transmitters in this bandthat are transmitting unwanted jamming signals.

The 900-928 MHZ frequency band is only a single example of where jammingis a significant problem. Jamming problems are not limited to this bandand can be a potential problem at any frequency.

What is needed is an improved method and system for ensuring thereception of a modulated signal in an environment with potentiallymultiple jamming signals.

What is also needed is a method and system for generating a modulatedsignal that is resistant to interference during transmission over acommunications link.

What is further needed is a method and system for generating a modulatedsignal that has a higher inherent jamming margin than standardmodulation schemes (e.g. AM, FM, PM, etc.), without substantiallyincreasing system complexity and cost.

SUMMARY OF THE INVENTION

The present invention is directed to methods and systems for ensuringthe reception of a communications signal, and applications thereof.

According to an embodiment, the present invention accepts a modulatingbaseband signal and generates a plurality of redundant spectrums, whereeach redundant spectrum includes the information content to representthe modulating baseband signal. In other words, each redundant spectrumincludes the necessary amplitude, phase, and frequency information toreconstruct the modulating baseband signal.

In an embodiment, the redundant spectrums are generated by modulating afirst oscillating signal with a modulating baseband signal, resulting ina modulated signal with an associated modulated spectrum. The modulatedsignal can be the result of any type of modulation including but notlimited to: amplitude modulation, frequency modulation, phasemodulation, or combinations thereof. The information (that representsthe modulating baseband signal) in the modulated spectrum is thenreplicated to thereby achieve the plurality of redundant spectrums thatare substantially identical in information content to the modulatedspectrum. The information in the modulated spectrum can be replicated bymodulating the associated modulated signal with a second oscillatingsignal. In one embodiment, the modulated signal is phase modulated withthe second oscillating signal, where the phase of the modulated signalis shifted as a function of the second oscillating signal. In analternate embodiment, the modulated signal is frequency modulated withthe second oscillating signal, where the frequency of the modulatedsignal is shifted as a function of the second oscillating signal.

In an alternate embodiment, the redundant spectrums are generated bymodulating a first oscillating signal with a modulated signal. Themodulated signal is generated by modulating a second oscillating signalwith the modulating baseband signal. As above, the modulated signal canbe the result of any type of modulation including but not limited to:amplitude modulation, frequency modulation, phase modulation, orcombinations thereof. In one embodiment, the first oscillating signal isphase modulated with the modulated signal, where the phase of the firstoscillating signal is varied as a function of the modulated signal. Inan alternate embodiment, the first oscillating signal is frequencymodulated with the modulated signal, where the frequency of the firstoscillating signal is varied as function of the modulated signal.

In one embodiment, the redundant spectrums are processed before beingtransmitted over a communications link. The spectrum processing caninclude selecting a subset of the redundant spectrums in order to reducethe bandwidth occupied by the redundant spectrums. The spectrumprocessing can also include attenuating any unmodulated tone associatedwith the redundant spectrums that is not desired to be transmitted.Finally, spectrum processing can include frequency upconversion andamplification, prior to transmission over the communications medium.

It is expected but not required that the redundant spectrums will begenerated at a first location and transmitted to a second location overa communications medium. At the second location, a demodulated basebandsignal is recovered from the received redundant spectrums. The recoveryof a substantially error-free demodulated baseband signal includestranslating the received redundant spectrums to a lower frequency,isolating the redundant spectrums into separate channels, and extractingthe substantially error-free demodulated baseband signal from theisolated redundant spectrums. In one embodiment, extracting theerror-free demodulated baseband signal includes demodulating each of theisolated redundant spectrums, analyzing each of the demodulated basebandsignals for errors, and selecting a demodulated baseband signal that issubstantially error-free. An error-free demodulated baseband signal isone that is substantially similar to the modulating baseband signal usedto generated the redundant spectrums at the first location. Detectingerrors in the demodulated baseband signals can be done in a number ofways including using cyclic redundancy check (CRC), parity check, checksum, or any other error detection scheme.

An advantage of transmitting a plurality of redundant spectrums over acommunications medium is that the intended demodulated baseband signalcan be recovered even if one or more of the redundant spectrums arecorrupted during transmission. The intended demodulated baseband signalcan be recovered because each redundant spectrum contains the necessaryamplitude, phase, and frequency information to reconstruct themodulating baseband signal.

Furthermore, the bandwidth occupied by the redundant spectrums can becontrolled by selecting a subset of redundant spectrums fortransmission. Also, the frequency spacing between the redundantspectrums can be controlled by adjusting the frequency of the secondoscillating signal. Therefore, the bandwidth occupied by the redundantspectrum is tunable, and easily customized by a communications systemdesigner.

Further features and advantages of the invention, as well as thestructure and operation of various embodiments of the invention, aredescribed in detail below with reference to the accompanying drawings.The drawing in which an element first appears is typically indicated bythe leftmost character(s) and/or digit(s) in the corresponding referencenumber.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to theaccompanying drawings wherein:

FIGS. 1A-1G depict various electrical signals in the time domain andfrequency domain;

FIG. 2A depicts an exemplary environment in which the present inventionis useful;

FIGS. 2B-2D depict various signals from the environment of FIG. 2A;

FIG. 3A depicts a flowchart 300, which illustrates generating redundantspectrums according to the present invention;

FIGS. 3B-3E depict several signal diagrams associated with flowchart300;

FIG. 3F depicts a structural block diagram corresponding to flowchart300 according an embodiment of the present invention;

FIG. 4A depicts flowchart 400, which illustrates generating redundantspectrums by replicating a modulated spectrum according to an embodimentof the present invention;

FIGS. 4B-4H depict several signal diagrams associated with flowchart 400according to an embodiment of the present invention;

FIG. 4I depicts a structural block diagram corresponding to flowchart400 according to an embodiment of the present invention;

FIG. 5A depicts a flowchart 500, which illustrates amplitude modulatingan oscillating signal with a modulating baseband signal according to anembodiment of the present invention;

FIGS. 5B-5G depict several signal diagrams that are associated withflowchart 500 according to an embodiment of the present invention;

FIG. 5H depicts a structural block diagram associated with flowchart 500according an embodiment of the present invention;

FIG. 6A depicts a flowchart 600, which illustrates frequency modulatingan oscillating signal with a modulating baseband signal according to anembodiment of the present invention;

FIGS. 6B-6G depict several signal diagrams that are associated withflowchart 600 according to an embodiment of the present invention;

FIG. 6H depicts a structural block diagram associated with flowchart 600according to an embodiment of the present invention;

FIG. 7A depicts a flowchart 700, which illustrates phase modulating anoscillating signal with a modulating baseband signal;

FIGS. 7B-7G depict several signal diagrams that are associated withflowchart 700;

FIG. 7H depicts a structural block diagram associated with flowchart 700according to an embodiment of the present invention;

FIG. 8A depicts a flowchart 800, which illustrates phase modulating amodulated signal with a second oscillating signal to generate redundantspectrums according to an embodiment of the present invention;

FIGS. 8B-8H depict several signal diagrams that are associated withflowchart 800 according to an embodiment of the present invention;

FIG. 8I depicts a structural block diagram associated with flowchart 800according to an embodiment of the present invention;

FIG. 8J depicts a flowchart 824, which illustrates frequency modulatinga modulated signal with an oscillating signal according to an embodimentof the present invention;

FIG. 8K depicts a structural block diagram associated with flowchart 824according to an embodiment of the present invention;

FIG. 8K-1 depicts a structural block diagram associated with generator318 according to an embodiment of the present invention;

FIG. 9 illustrates a structural implementation of an AM modulatoraccording to one embodiment of the present invention;

FIG. 10 illustrates a structural implementation of a FM modulatoraccording to one embodiment of the present invention;

FIGS. 11A-E illustrate a structural implementation of a phase modulatoraccording to one embodiment of the present invention;

FIGS. 12A-E illustrate a structural implementation of phase modulator1200, which is an example implementation of PM modulator 820 accordingto an embodiment of the present invention;

FIG. 13A depicts a flowchart 1300, which illustrates generatingredundant spectrums by phase modulating an oscillating signal with amodulated signal according to one embodiment of the present invention;

FIGS. 13B-K depict several signal diagrams that are associated withflowchart 1300 according to an embodiment of the present invention;

FIG. 13L depicts a structural block diagram associated with flowchart1300 according to an embodiment of the present invention;

FIG. 13M depicts a flowchart 1334, which illustrates generatingredundant spectrums by frequency modulating an oscillating signal with amodulated signal according an embodiment of the present invention;

FIG. 13N depicts a structural block diagram associated with flowchart1334 according to one embodiment of the present invention;

FIG. 13N-1 depicts a structural block diagram associated with generator318 according to an embodiment of the present invention;

FIG. 13O depicts a flowchart 1342, which illustrates generatingredundant spectrums by modulating a first modulated signal with a secondmodulated signal;

FIGS. 13P-V depict several signal diagrams that are associated withflowchart 1342 according to an embodiment of the present invention;

FIG. 13W depicts a structural block diagram associated with flowchart1342 according to one embodiment of the present invention;

FIG. 14A depicts flowchart 1400, which illustrates processing redundantspectrums according to one embodiment of the present invention;

FIGS. 14B-C depict signal diagrams that are associated with flowchart1400 according to an embodiment of the present invention;

FIG. 14D depicts a structural block diagram associated flowchart 1400according to an embodiment of the present invention.

FIG. 15A depicts flowchart 1500, which illustrates processing redundantspectrums according to an embodiment of the present invention;

FIGS. 15B-F depict several signal diagrams that are associated withflowchart 1500 according to an embodiment of the present invention;

FIG. 15G depicts a structural block diagram associated with flowchart1500 according to an embodiment of the present invention;

FIGS. 16A-F depict several signal diagrams associated with flowchart1500 according to one embodiment of the present invention;

FIGS. 16G-I depict structural embodiments and implementations for afrequency up-converter;

FIGS. 16J-R depict several signal diagrams associated with theup-converter system 1620 described in FIGS. 16G-I;

FIG. 17A depicts flowchart 1700, which illustrates recovering ademodulated baseband signal from redundant spectrums according to anembodiment of the present invention;

FIGS. 17B-H depict several signal diagrams that are associated withflowchart 1700 according to an embodiment of the present invention;

FIG. 17I depicts structural block diagram associated with flowchart 1700according to an embodiment of the present invention;

FIG. 18A depicts flowchart 1800, which illustrates translating redundantspectrums to a lower frequency according to an embodiment of the presentinvention;

FIGS. 18B-18H depict several signal diagrams that are associated withflowchart 1800 according to an embodiment of the present invention;

FIG. 18I depicts a structural block diagram associated with flowchart1700 according to one embodiment of the present invention;

FIGS. 19A and 19A1 depict a structural embodiments and implementationsfor frequency down-conversion according to embodiments of the presentinvention;

FIGS. 19B-F depict several signal diagrams that are associated with auniversal frequency translation (UFT) module 1902 in FIG. 19A.

FIG. 20A depicts flowchart 2000, which illustrates isolating redundantspectrums into a separate channels according to an embodiment of thepresent invention;

FIG. 20B depicts a structural block diagram associated with flowchart2000 according to an embodiment of the present invention;

FIG. 20C depicts a structural embodiment of receiver 1730 using UFDmodules;

FIG. 21A depicts flowchart 2100, which illustrates extracting ademodulated baseband signal from redundant spectrums according to anembodiment of the present invention;

FIGS. 21B-H depict several signal diagrams that are associated withflowchart 2100 according to an embodiment of the present invention;

FIG. 21I depicts a structural block diagram associated with flowchart2100, according to one embodiment of the present invention;

FIG. 22A depicts a flowchart 2200, which illustrates selecting anerror-free demodulated baseband signal using a process of eliminationaccording to an embodiment of the present invention;

FIG. 22B depicts a flowchart 2222, which illustrates selecting anerror-free demodulated baseband signal using a process of eliminationaccording to an embodiment of the present invention;

FIG. 23 depicts a structural block diagram of an embodiment of errorcheck module 2114, according to one embodiment of the present invention;and

FIG. 24 depicts the conceptual representation of a UnifiedDown-Converting and Filtering Module (UDF);

FIG. 25 depicts Table 2502 associated with UDF module 2622; and

FIG. 26 illustrates a structural implementation of a UFD module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Table of Contents

1 Terminology

2 Overview of the Invention

3 Example Environment

4 Generating Redundant Spectrums That Have Substantially the SameInformation content According to Embodiments of the Present Invention

4.1 High Level Description

4.1.1 Operational Description

4.1.2 Structural Description

4.2 Example Embodiments

4.2.1 Generating Redundant Spectrums by Replicating a Modulated Spectrum

4.2.1.1 High Level Description

4.2.1.1.1 Operational Description

4.2.1.1.2 Structural Description

4.2.1.2 Example Components of the Embodiments

4.2.1.2.1 First Stage Modulator

 4.2.1.2.1.1 First Embodiment: Amplitude Modulation Mode

 4.2.1.2.1.1.1 Operational Description

 4.2.1.2.1.1.2 Structural Description

4.2.1.2.1.2 Second Embodiment: Frequency Modulation Mode

 4.2.1.2.1.2.1 Operational Description

 4.2.1.2.1.2.2 Structural Description

 4.2.1.2.1.3 Third embodiment: Phase Modulation Mode

 4.2.1.2.1.3.1 Operational Description

 4.2.1.2.1.3.2 Structural Description

 4.2.1.2.1.4 Other Embodiments

4.2.1.2.2 Second Stage Modulator (Replicator Modulator)

 4.2.1.2.2.1 First embodiment: Replicating the Modulated Spectrum byPhase Modulating the Modulated Signal.

 4.2.1.2.2.1.1 Operational Description

 4.2.1.2.2.1.2 Structural Description

 4.2.1.2.2.2 Second embodiment: Replicating the Modulated Spectrum byFrequency Modulating the Modulated Signal.

 4.2.1.2.2.2.1 Operational Description

 4.2.1.2.2.2.2 Structural Description

 4.2.1.2.2.3 Other Embodiments

4.2.1.3 Implementation Examples

4.2.1.3.1 First Stage Modulator

 4.2.1.3.1.1 AM Modulator as a Transistor Oscillator with a VariableResistor

 4.2.1.3.1.2 FM Modulator as a Voltage Controlled Crystal Oscillator

 4.2.1.3.1.3 PM Modulator as a Tunable Filter

 4.2.1.3.1.4 Other Implementations

4.2.1.3.2 Second Stage Modulator (Replicator Modulator)

 4.2.1.3.2.1 PM Modulator as a Tunable Filter

 4.2.1.3.2.2 Other Implementations for a PM modulator

 4.2.1.3.2.3 Other Implementations for the Second Stage Modulator

4.2.2 Generating Redundant Spectrums by Modulating an Oscillating SignalWith a Modulated Signal

4.2.2.1 Generating Redundant Spectrums by Phase Modulating anOscillating Signal With a Modulated Signal

4.2.2.1.1 High Level Description

 4.2.2.1.1.1 Operational Description

 4.2.2.1.1.2 Structural Description

4.2.2.1.2 Example Components of the Embodiments

 4.2.2.1.2.1 First Stage Modulator

 4.2.2.1.2.1.1 First embodiment: Amplitude Modulation (AM), includingAmplitude Shift Keying (ASK) Mode

 4.2.2.1.2.1.2 Second embodiment: Frequency Modulation (FM), includingFrequency Shift Keying (FSK) Mode

 4.2.2.1.2.1.3 Third embodiment: Phase Modulation (PM) and Phase ShiftKeying (PSK) Mode

 4.2.2.1.2.1.4 Other Embodiments

4.2.2.1.3 Implementation Examples

 4.2.2.1.3.1 First Stage Modulator 1328

 4.2.2.1.3.1.1 AM Modulator as a Variable Gain Transistor Amplifier

 4.2.2.1.3.1.2 FM Modulator as a Voltage Controlled Crystal Oscillator

 4.2.2.1.3.1.3 Phase Modulator as Tunable Filter

 4.2.2.1.3.1.4 Other Implementations

 4.2.2.1.3.2 Phase Modulator 1332 as a tunable filter

 4.2.2.1.3.2.1 Phase Modulator 1332 as a Tunable Filter

 4.2.2.1.3.2.2 Other Implementations

4.2.2.2 Generating Redundant Spectrums by Frequency Modulating anOscillating Signal With a Modulated Signal

4.2.2.2.1 High Level Description

 4.2.2.2.1.1 Operational Description

 4.2.2.2.1.2 Structural Description

4.2.2.2.2 Example Components of the Embodiments

 4.2.2.2.2.1 First stage modulator

4.2.2.2.3 Implementation Examples of the Embodiments

 4.2.2.2.3.1 First Stage Modulator

 4.2.2.2.3.1.1 AM Modulator as a Variable Gain Amplifier

 4.2.2.2.3.1.2 FM Modulator as a Voltage Controlled Oscillator

 4.2.2.2.3.1.3 PM Modulator as a Tunable Filter

 4.2.2.2.3.1.4 Other Implementations

 4.2.2.2.3.2 Frequency Modulator

 4.2.2.2.3.2.1 Frequency Modulator 1340 as a VCXO

 4.2.2.2.3.2.2 Other Implementations

4.2.2.3 Other Embodiments

4.2.3 Generating Redundant Spectrums by Modulating a First ModulatingSignal with a Second Modulating Signal

4.2.3.1 High Level Description

 4.2.3.1.1 Operational Description

 4.2.3.1.2 Structural Description

5 Spectrum Conditioning Prior to Transmission Over a Communicationsmedium

5.1 High Level Description

5.1.1 Operational Description

5.1.2 Structural Description

5.2 Example Embodiments

5.2.1 First Embodiment of Processing Redundant Spectrums

5.2.1.1 Operational Description

5.2.1.2 Structural Description

5.2.2 Other Embodiments

5.2.3 Implementation Examples

5.2.3.1 Frequency Up-conversion

5.2.3.2 Other Implementations

6 Recovering a Demodulated Baseband Signal from the Redundant Spectrumsthat have Substantially the Same Information content

6.1 High Level Description

6.1.1 Operational Description

6.1.2 Structural Description

6.2 Example Embodiments

6.2.1 Down-conversion

6.2.1.1 Down-conversion by Mixing Redundant Spectrums with anOscillating Signal

6.2.1.1.1 Operational Description

6.2.1.1.2 Structural Description

6.2.1.2 Down-conversion Using a Universal Frequency Translation Module

6.2.1.3 Other Embodiments

6.2.2 Spectrum Isolation

6.2.2.1 Spectrum Isolation by Filtering Redundant Spectrums

6.2.2.1.1 Operational Description

6.2.2.1.2 Structural Description

6.2.2.2 Down-conversion and Spectrum Isolation using a UnifiedDown-converting and Filtering Module (UDF)

6.2.2.3 Other Embodiments

6.2.3 Signal extraction

6.2.3.1 Signal extraction by Demodulation, with Error Checking and/orError Correction

6.2.3.1.1 Operational Description

6.2.3.1.2 Structural Description

6.2.3.2 Other Embodiments

1. Terminology

Various terms used in this application are generally described in thissection. The description in this section is provided for illustrativeand convenience purposes only, and is not limiting. The meaning of theseterms will be apparent to persons skilled in the relevant art(s) basedon the entirety of the teachings provided herein. These definitions maybe discussed throughout the specification with additional detail.

Analog signal: A signal that is constant or continuously variable, ascontrasted to a signal that changes between discrete states.

Baseband: A frequency band occupied by any generic information signaldesired for transmission and/or reception.

Baseband signal: Any generic information signal desired for transmissionand/or reception.

Carrier frequency: The frequency of a carrier signal. Typically, it isthe center frequency of a transmission signal that is generallymodulated.

Carrier signal: An EM wave having at least one characteristic that maybe varied by modulation, that is capable of carrying information viamodulation.

Demodulated baseband signal: A signal that results from processing amodulated signal. In some cases, for example, the demodulated basebandsignal results from demodulating an intermediate frequency (IF)modulated signal, which results from down converting a modulated carriersignal. In another case, a signal that results from a combineddown-conversion and demodulation step.

Digital signal: A signal that changes between discrete states, ascontrasted to a signal that is continuous. For example, the voltage of adigital signal may shift between discrete levels.

Electromagnetic spectrum: A spectrum comprising waves characterized byvariations in electric and/or magnetic fields. Such waves may bepropagated in any communication medium, both natural and manmade,including but not limited to air, space, wire, cable, liquid, waveguide,microstrip, stripline, optical fiber, etc. The EM spectrum includes allfrequencies greater than zero hertz.

EM signal: A signal in the EM spectrum. Also generally called an EMwave. Unless stated otherwise, all signals discussed herein are EMsignals, even when not explicitly designated as such.

Jamming signal: Refers to any unwanted signal, regardless of origin,that may interfere with the proper reception and reconstruction of anintended signal.

Modulating baseband signal: Any generic information signal that is usedto modulate an oscillating signal, or carrier signal.

Redundant Spectrums: A spectrum that includes the necessary amplitude,phase, and frequency information to construct a modulating basebandsignal.

2. Overview of the Present Invention

The present invention is directed to methods and systems for ensuringthe reception of a communications signal, and applications thereof.

According to an embodiment, the present invention accepts a modulatingbaseband signal and generates a plurality of redundant spectrums, whereeach redundant spectrum includes the information content to representthe modulating baseband signal. In other words, each redundant spectrumincludes the necessary amplitude, phase, and frequency information toreconstruct the modulating baseband signal.

In an embodiment, the redundant spectrums are generated by modulating afirst oscillating signal with a modulating baseband signal, resulting ina modulated signal with an associated modulated spectrum. The modulatedsignal can be the result of any type of modulation including but notlimited to: amplitude modulation, frequency modulation, phasemodulation, or combinations thereof. The information in the modulatedspectrum can then replicated to thereby achieve the plurality ofredundant spectrums that are substantially identical in informationcontent to the modulated spectrum. The modulated spectrum can bereplicated by modulating the associated modulated signal with a secondoscillating signal. In one embodiment, the modulated signal is phasemodulated with the second oscillating signal, where the phase of themodulated signal is shifted as a function of the second oscillatingsignal. In an alternate embodiment, the modulated signal is frequencymodulated with the second oscillating signal, where the frequency of themodulated signal is shifted as a function of the second oscillatingsignal. Those skilled in the arts will recognize that other modulationembodiments can be used to replicate a modulated spectrum including butnot limited to amplitude modulation. Such other embodiments fall withinthe scope and spirit of the present invention.

In an alternate embodiment, the redundant spectrums are generated bymodulating a first oscillating signal with a modulated signal. Themodulated signal is generated by modulating a second oscillating signalwith the modulating baseband signal. As above, the modulated signal canbe the result of any type of modulation including but not limited to:amplitude modulation, frequency modulation, phase modulation, orcombinations thereof. In one embodiment, the first oscillating signal isphase modulated with the modulated signal, where the phase of the firstoscillating signal is varied as a function of the modulated signal. Inan alternate embodiment, the first oscillating signal is frequencymodulated with the modulated signal, where the frequency of the firstoscillating signal is varied as function of the modulated signal.

In one embodiment, the redundant spectrums are processed before beingtransmitted over a communications link. The spectrum processing caninclude selecting a subset of the redundant spectrums in order to reducethe bandwidth occupied by the redundant spectrums. The spectrumprocessing can also include attenuating any unmodulated tone associatedwith the redundant spectrums that is not desired to be transmitted.Finally, spectrum processing can include frequency upconversion andamplification, prior to transmission over the communications medium.

It is expected but not required that the redundant spectrums will begenerated at a first location and transmitted to a second location overa communications medium. At the second location, a demodulated basebandsignal is recovered from the received redundant spectrums. The recoveryof a substantially error-free demodulated baseband signal includestranslating the received redundant spectrums to a lower frequency,isolating the redundant spectrums into separate channels, and extractingthe substantially error-free demodulated baseband signal from theisolated redundant spectrums. In one embodiment, extracting theerror-free demodulated baseband signal includes demodulating each of theisolated redundant spectrums, analyzing each of the demodulated basebandsignals for errors, and selecting a demodulated baseband signal that issubstantially error-free. An error-free demodulated baseband signal isone that is substantially similar to the modulating baseband signal usedto generated the redundant spectrums at the first location. Detectingerrors in the demodulated baseband signals can be done in a number ofways including using cyclic redundancy check (CRC), parity check, checksum, or any other error detection scheme.

An advantage of transmitting a plurality of redundant spectrums over acommunications medium is that the intended demodulated baseband signalcan be recovered even if one or more of the redundant spectrums arecorrupted during transmission. The intended demodulated baseband signalcan be recovered because each redundant spectrum contains the necessaryamplitude, phase, and frequency information to reconstruct themodulating baseband signal.

Furthermore, the bandwidth occupied by the redundant spectrums can becontrolled by selecting a subset of redundant spectrums fortransmission. Also, the frequency spacing between the redundantspectrums can be controlled by adjusting the frequency of the secondoscillating signal. Therefore, the bandwidth occupied by the redundantspectrum is tunable, and easily customized by a communications systemdesigner.

3. Example Environment

FIG. 2A illustrates an example communication system 201 in which thepresent invention is useful. The communications system 201 includes: abasestation 202, a dispatcher 204, a driver 210, a handset 214, andsignals 206, 208, and 212.

In an embodiment, the dispatcher 204 and the driver 210 are employees ofa delivery company and utilize wireless communications to operate theirdelivery business. For example, the dispatcher 204 may send deliveryinstructions over a private paging network to the driver 210. Thebasestation 202 is part of a wireless phone network and routes calls tohandsets within its coverage area, including the handset 214. In oneexample, basestation 202 and dispatcher 204 utilize the same frequencyband.

In FIG. 2A, the dispatcher 204 is shown as sending a modulated signal206 to the driver 210. The modulated signal 206 may be a page messagewith current delivery instructions for the driver 210, and has acorresponding modulated spectrum 214 illustrated in FIG. 2B.Simultaneously, the basestation 202 is sending a test signal 208, whichis a pure sinusoidal tone at frequency f_(jam). The test signal 208 hasa spectrum 216 illustrated in FIG. 2C. Since the driver 210 is mobile,the driver 210 will arrive at a geographic location where signals 206and 208 combine to form signal 212. As shown in FIG. 2D, signal 212includes the combination of spectrums 214 and 216.

The driver 210 must receive and process the entire spectrum 214 toproperly reconstruct the page message from the dispatcher 204. To do so,the sine waves in spectrum 214 must be summed together with the correctamplitude and phase. If the power in unwanted (jamming) spectrum 216becomes sufficiently large, the sine wave summation will be inaccurate,and the driver 210 will not be able to recover the message in datasignal 206. The maximum power level of the spectrum 214 that can betolerated is defined by the “jamming margin” of the driver 210'sreceiver. FIG. 2D illustrates a jamming margin 218 that is equal to −3dB, which could be possible using FM modulated signals. That is, if theinterfering spectrum 216 power level is within 3 dB of the spectrum 214power level, then the message carried in spectrum 214 cannot berecovered intact at the driver 210's receiver.

4 Generating Redundant Spectrums That Have Substantially the SameInformation Content According to Embodiments of the Present Invention

The following discussion describes embodiments for generating redundantspectrums that have substantially the same information content accordingto the present invention. The invention description includes a highlevel description, example embodiments, and implementation examples ofthe present invention.

4.1 High Level Description

This section (including subsections) provides a high level descriptionfor generating redundant spectrums that have substantially the sameinformation content according to an embodiment of the present invention.The following discussion includes an operational process for generatingredundant spectrums according to one embodiment of the presentinvention. Also, a structural description for achieving this process isdescribed herein for illustrative purposes, and is not meant to limitthe invention in any way. In particular, the process described in thissection can be achieved using any number of structural implementations,at least one of which is described in this section. The details of thestructural description will be apparent to those skilled in the artbased on the teachings herein.

4.1.1 Operational Description

FIG. 3A depicts a flowchart 300 that illustrates operational steps forgenerating multiple redundant spectrums that have substantially the sameinformation content according to an embodiment of the present invention.Each redundant spectrum carries the information necessary to at leastsubstantially or completely reconstruct the modulating baseband signal.In the following discussion, the steps in FIG. 3A will be discussedrelative to the example signal diagrams shown in FIGS. 3B-3E.

In step 302, a modulating baseband signal 308 (shown in FIG. 3B) isaccepted. Modulating baseband signal 308 is a representative informationsignal that is shown for illustrative purposes only, and is not intendedto limit the present invention in any way. Modulating baseband signal308 is represented as an analog signal in FIG. 3B, but modulatingbaseband signal 308 could alternatively be a digital signal, or acombination thereof.

Modulating baseband signal 308 could be a voltage (or current)characterization of any number of real world occurrences. For example,without limiting the invention, a typical analog modulating basebandsignal is the voltage output of a microphone for a given acousticalinput, such as a voice input. Again, without limiting the invention, atypical digital modulating baseband signal may be a digital bit streamthat represents a digitized voice signal, or a digital bit stream ofcomputer data.

FIG. 3C illustrates the frequency spectrum 310 of the modulatingbaseband signal 308. As discussed earlier, the frequency spectrum of anyelectrical signal illustrates the relative amplitude of the sine wavesthat when summed together with the correct phase will sufficientlyreconstruct the electrical signal in the time domain. In other words,the spectrum 310 contains the necessary amplitude, phase, and frequencyinformation to distinctly represent the modulating baseband signal 308.As such, the modulating baseband signal 308 and the spectrum 310 areequivalent representations of the same electrical signal.

The spectrum 310 is represented in FIG. 3C as having a generic shape.Those skilled in the relevant art(s) will recognize that the actualshape of the spectrum 310 will depend on a specific modulating basebandsignal 308 input. The spectrum 310 has a bandwidth B, meaning thatfrequencies beyond B (Hz) have substantially negligible amplitude in thespectrum 310, and thus can typically be ignored when reconstructingmodulating baseband signal 308. Spectrums (like spectrum 310) that areunmodulated and are often referred to as “baseband” spectrums. This isin contrast to modulated spectrums that are typically located at muchhigher frequencies.

FIG. 3D illustrates the spectrum 310 and its image spectrum 311. Theimage spectrum 311 is the mirror image about DC (0 Hz) of the spectrum310. The image spectrum 311 does not actually exist and hence the reasonfor the dotted line representation in FIG. 3D. Those skilled in therelevant art(s) often depict the image spectrum for a baseband signal topredict the shape and bandwidth of the baseband signal once it has beenup-converted to a higher frequency using a modulation technique, as willbe seen in later sections.

In step 304, multiple redundant spectrums 312 a-n (FIG. 3E) aregenerated based upon the modulating baseband signal 308. Each redundantspectrum 312 a-n contains the necessary amplitude, phase, and frequencyinformation to substantially reconstruct the modulating baseband signal308. That is, each redundant spectrum 312 a-n contains at leastsubstantially the same information content of spectrum 310. There is nonumerical limit to the number of spectrums generated, and the “a-n”designation is not meant to suggest a limit in any way.

In one embodiment, each redundant spectrum 312 a-n includes an imagespectrum. In an alternate embodiment, each redundant spectrum 312 a-n isprocessed to suppress the image spectrum resulting in a bandwidth of B(Hz) for each redundant spectrum 312 a-n.

In one embodiment, the redundant spectrums 312 a-n are at asubstantially higher frequency than the spectrum 310 which exists atbaseband. This is represented by the break 314 in the frequency axis ofFIG. 3E.

In one embodiment, the amplitude of each redundant spectrum 312 a-b,d-n“rolls off” with increasing frequency distance from the center redundantspectrum 312 c. For example, redundant spectrums 312 b,d have a loweramplitude than center redundant spectrums 312 c as is illustrated inFIG. 3E. However, the relative amplitude and phase of the frequencycomponents within a given spectrum is conserved, and therefore, eachredundant spectrum 312 a-n may still be used to reconstruct themodulating baseband signal 308 despite the amplitude rolloff. As shown,FIG. 3E depicts this amplitude rolloff relative to the distance from thecenter spectrum. But for convenience of illustration, the amplituderolloff will not be depicted in subsequent figures that are directed atredundant spectrums.

In step 306, the redundant spectrums 312 a-n are transmitted over acommunications medium. It is expected, but not required, that theredundant spectrums 312 a-n would be generated at a first location andsent to a second location over the communications medium. At the secondlocation, the redundant spectrums would be processed to recover themodulating baseband signal 308. In one embodiment, the communicationsmedium is an over-the-air wireless communications link. In otherembodiments, the communications medium can include the following: wire,optical link, liquid, or any other communications medium.

As stated above, each redundant spectrum 312 a-n contains the necessaryamplitude, phase, and frequency information to substantially reconstructthe modulating baseband signal 308. As such, even if one or more of theredundant spectrums 312 a-n are corrupted by a jamming signal in thecommunications medium, the modulating baseband signal 308 can still berecovered from any of the other redundant spectrums 312 a-n that havenot been corrupted.

For illustrative purposes, the operation of the invention is oftenrepresented by flowcharts, such as flowchart 300 in FIG. 3A. It shouldbe understood, however, that the use of flowcharts is for illustrativepurposes only, and is not limiting. For example, the invention is notlimited to the operational embodiment(s) represented by the flowcharts.Instead, alternative operational embodiments will be apparent to personsskilled in the relevant art(s) based on the discussion contained herein.Also, the use of flowcharts should not be interpreted as limiting theinvention to discrete or digital operation. In practice, as will beappreciated by persons skilled in the relevant art(s) based on theherein discussion, the invention can be achieved via discrete orcontinuous operation, or a combination thereof. Further, the flow ofcontrol represented by the flowcharts is provided for illustrativepurposes only. As will be appreciated by persons skilled in the relevantart(s), other operational control flows are within the scope and spiritof the present invention.

4.1.2 Structural Description

FIG. 3F illustrates a block diagram of transmission system 317 accordingto an embodiment of the present invention. Transmission system 317comprises a generator 318 and a (optional) medium interface 320.Transmission system 317 accepts a modulating baseband signal 308 andtransmits multiple redundant spectrums 312 a-n in the manner shown inoperational flowchart 300. In other words, the transmission system 317is the structural embodiment for performing the operational steps inflowchart 300. However, it should be understood that the scope andspirit of the present invention includes other structural embodimentsfor performing steps in flowchart 300. The specifics of these otherstructural embodiments will be apparent to persons skilled in therelevant art(s) based on the discussion contain herein. Flowchart 300will re-visited to further illustrate the present invention in view ofthe structural components in transmission system 317.

In step 302, the generator 318 accepts the modulating baseband signal308, which has a corresponding frequency spectrum 310. In step 304, thegenerator 318 generates multiple redundant spectrums 312 a-n. Eachredundant spectrum 312 a-n contains the necessary amplitude, phase, andfrequency information to substantially reconstruct the modulatingbaseband signal 308. As such, each redundant spectrum 312 a-n could beprocessed to reconstruct the modulating baseband signal 308.

In step 306, the (optional) medium interface module 320 transmits theredundant spectrums 312 a-n over a communications medium 322. In anembodiment, the communications medium is a wireless link, and (optional)medium interface module 320 is an antenna which transmits the redundantspectrums into free space. In other embodiments, the (optional) mediuminterface module 320 can be (but is not limited to) one of thefollowing: a modem, connector, or any other device that can be used tointerface to a communications medium.

4.2 Example Embodiments

The following discussion describes example embodiments for generatingredundant spectrums that have substantially the same informationcontent, where the information content in each redundant spectrumrepresents a modulating baseband signal. A first embodiment generatesredundant spectrums by replicating a modulated spectrum. The redundantspectrums can be replicated by modulating a modulated signal with anoscillating signal. A second embodiment generates redundant spectrums bymodulating an oscillating signal with a modulated signal. A thirdembodiment generates redundant spectrums by modulating a first modulatedsignal with a second modulated signal. These embodiments are providedfor illustrative purposes, and are not limiting. Other embodiments willbe apparent to persons skilled in the art(s) based on teachingscontained herein.

4.2.1 Generating Redundant Spectrums by Replicating a Modulated Spectrum

The following discussion is directed to a method and system forgenerating redundant spectrums by replicating a modulated spectrumaccording to an embodiment the invention.

4.2.1.1 High Level Description

This section (including subsections) provides a high level descriptionfor generating redundant spectrums by replicating a modulated spectrum.The following discussion includes an exemplary operational process forgenerating redundant spectrums by replicating a modulated spectrum.Also, a structural description for achieving this process is describedherein for illustrative purposes, and is not meant to limit theinvention in any way. In particular, the process described in thissection can be achieved using any number of structural implementations,at least one of which is described in this section. The details of thestructural description will be apparent to those skilled in the artbased on the teachings herein.

4.2.1.1.1 Operational Description

FIG. 4A depicts a flowchart 400 which illustrates in greater detail theflowchart 300 of FIG. 3A. In particular flowchart 400 illustrates theoperation of step 304 in greater detail. As described above, in step304, multiple redundant spectrums are generated based on the input ofmodulating baseband signal 308. In the following discussion, the stepsin flowchart 400 will be discussed in relation to the example signaldiagrams shown in FIGS. 4B-4G.

In step 302, the modulating baseband signal 308 is accepted. FIG. 4Billustrates an example modulating baseband signal 308, and FIGS. 4Cillustrates a corresponding the spectrum 310 and image spectrum 311associated with modulating baseband signal 308. It is noted that step302, signal 308, and spectrums 310, 311 described here are the same asthose described above and shown in FIGS. 3A-3D. They are re-illustratedhere for convenience.

In step 402, a first oscillating signal 408 (FIG. 4D) is generated. Thefirst oscillating signal 408 is typically a sinewave with acharacteristic frequency f₁. Other periodic waveforms could be usedincluding but not limited to square wave. As such, the first oscillatingsignal 408 has a frequency spectrum 410 that is substantially a tone atf₁ (FIG. 4E). Typically, f₁ for the first oscillating signal 408 is muchhigher than the highest frequency B in the modulating baseband signalspectrum 310, which is represented by the break 411 in the frequencyaxis in FIG. 4E. For example and without limitation, if the spectrum 310represents the frequency components of a typical voice signal, then thespectrum bandwidth B is approximately 3.5 KHz. Whereas, a typical firstoscillating signal f₁ will operate on the order of 100 MHZ. Theinvention is not limited to these example frequencies. In otherembodiments, other frequencies can be used.

In step 404, the first oscillating signal 408 is modulated with themodulating baseband signal 308, resulting in a modulated (mod) signal412 (FIG. 4F). The modulated signal 412 depicts the result of amplitudemodulation (AM), where the amplitude of the modulating baseband signal308 has been impressed on the amplitude of the first oscillating signal408. The use of AM is done for example purposes only, and is not meantto limit the invention in any way. Any type of modulation could be usedincluding but not limited to: amplitude modulation (AM), frequencymodulation (FM), phase modulation (PM), etc., or any combinationthereof. Various modulation schemes will be explored in section4.2.1.2.1.

The modulated signal 412 has a corresponding modulated spectrum 414(FIG. 4F) that is centered around f₁ which is the characteristicfrequency of the first oscillating signal 408. The modulated spectrum414 carries the necessary information to reconstruct the modulatingbaseband signal 308 at the receiver. (i.e. the modulated spectrum 414carries the necessary amplitude, phase, and frequency information toreconstruct the modulating baseband signal 308.)

The modulated spectrum 414 has a generic shape and bandwidth. Thoseskilled in the art will recognize that the actual shape and bandwidth ofmodulated spectrum 414 will depend on the specific modulating basebandsignal 308 and type of modulation used to modulate the first oscillatingsignal 408.

In step 406, the information contained in the modulated spectrum 414 isreplicated to produce redundant spectrums 416 a-n (FIG. 4H). Since eachredundant spectrum 416 a-n was replicated from the modulated spectrum414, each redundant spectrum 416 a-n carries the necessary informationto reconstruct the modulating baseband signal 308 at the receiver. (i.e.each redundant spectrum 416 carries the necessary amplitude, phase, andfrequency information to reconstruct the modulating baseband signal308.) As such, if one of the redundant spectrums 416 a-n is corrupted bya jamming signal, then the modulating baseband signal 308 can berecovered from one of the other redundant spectrums 416 a-n.

In step 306, the redundant spectrums 416 a-n are transmitted over acommunications medium. It is expected, but not required, that theredundant spectrums 312 a-n would be generated at a first location andsent to a second location over the communications medium. At the secondlocation, the redundant spectrums would be processed to reconstruct themodulating baseband signal 308. In one embodiment, the communicationsmedium is a wireless communications link.

Preferably, each redundant spectrum 416 a-n is offset from an adjacentredundant spectrum 416 a-n by an amount of Δf Hz. For example, spectrum416 c is centered at f₁ and spectrum 416 b is centered at (f₁−Δf).Theoretically, there is no limit to the number of redundant spectrums416 a-n created.

4.2.1.1.2 Structural Description

FIG. 4I illustrates a block diagram of generator 318 according to anembodiment of the present invention. Generator 318 comprises a firstoscillator 418, first stage modulator 420, and replicator 422. Generator318 accepts a modulating baseband signal 308 and generates multipleredundant spectrums 416 a-n in the manner shown in operational flowchart400. In other words, the generator 318 is a structural embodiment forperforming the operational steps in flowchart 400. However, it should beunderstood that the scope and spirit of the present invention includesother structural embodiments for performing steps in flowchart 400. Thespecifics of these other structural embodiments will be apparent topersons skilled in the relevant art(s) based on the discussion containedherein. Flowchart 400 will be re-visited to further illustrate thepresent invention in view of the structural components in generator 318.

In step 402, the first oscillator 418 generates the first oscillatingsignal 408. As discussed earlier, the first oscillating signal 408 issubstantially a sinusoid with frequency of f₁. Typically, the firstoscillating signal 408 has a frequency f₁ that is substantially higherthan the bandwidth B of spectrum 310, which represents the highestfrequency component in modulating baseband signal 308. For example, atypical bandwidth B for spectrum 310 is on the order of 10 KHz, and atypical value for f₁ is on the order of 100 MHZ.

In step 404, the modulator 420 modulates the first oscillating signal408 with the modulating baseband signal 308, resulting in the modulatedsignal 412 with corresponding modulated spectrum 414. As discussedearlier, the modulator 420 can be any type of modulator, as will beexplored in more detail in later sections. The modulated spectrum 414 iscentered around f₁, which is the frequency of first oscillating signal408. The modulated spectrum 414 includes the necessary amplitude, andfrequency information to reconstruct the modulating baseband signal 308.

In step 406, the replicator 422 replicates the information in themodulated spectrum 414 to generate redundant spectrums 416 a-n. Eachredundant spectrum 416 a-n includes substantially a copy of theinformation in the modulated spectrum 414, and thus can be used toreconstruct the modulating baseband signal 308. This is because eachredundant spectrum 416 a-n contains the relative amplitude, phase, andfrequency information to reconstruct the modulating baseband signal 308.

In step 306, (optional) medium interface 320 transmits redundantspectrums 416 a-n over communications medium 322. In one embodiment,communications medium 322 is a wireless link, and (optional) mediuminterface module 320 includes an antenna.

4.2.1.2 Example Component(s) of the Embodiment(s)

Various embodiments related to the method(s) and structure(s) describedabove are presented in this section (and its subsections). Specifically,the following discussion describes example embodiments of generatingredundant spectrums by replicating a modulated spectrum. Theseembodiments are described herein for purposes of illustration, and notlimitation. The invention is not limited to these embodiments. Alternateembodiments (including equivalents, extensions, variations, deviations,etc., of the embodiments described herein) will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.The invention is intended and adapted to include such alternateembodiments.

4.2.1.2.1 First Stage Modulator

The following discussion is directed to example embodiments of step 404in flowchart 400 (FIG. 4A), and the first stage modulator 420 (FIG. 4I).The example embodiments include but are not limited to: amplitudemodulation, frequency modulation, and phase modulation. These modulationschemes are described herein for illustrative purposes only. Othermodulation schemes, including different forms of the ones describedherein, will be apparent to persons skilled it the relevant art(s). Suchother modulation schemes are within the scope and spirit of the presentinvention.

4.2.1.2.1.1 First Embodiment: Amplitude Modulation (AM) Mode, IncludingAmplitude Shift Keying (ASK) Mode

The following discussion describes a method and system for generatingredundant spectrums using amplitude modulation, including amplitudeshift keying modulation.

4.2.1.2.1.1.1 Operational Description

FIG. 5A depicts a flowchart 500 constituting an embodiment of theflowchart 400 of FIG. 4A. The embodiment depicted in flowchart 500describes amplitude modulation(AM), which includes amplitude shiftkeying modulation (ASK). In the following discussion, the steps inflowchart 500 will be discussed in relation to the example signaldiagrams shown in FIGS. 5B-5G. FIGS. 5B-5D illustrate AM, and FIGS.5E-5G illustrate ASK modulation.

In step 302, the modulating baseband signal 308 is accepted. Themodulating baseband signal 308 has been previously been described asbeing either an analog or digital signal. For AM, the modulatingbaseband signal 308 is an analog signal, which is illustrated bymodulating baseband signal 508 a in FIG. 5B. For ASK modulation, themodulating baseband signal 308 is a digital signal, which is illustratedby modulating baseband signal 508 b in FIG. 5E.

In step 402, the first oscillating signal 408 is generated. As discussedpreviously, first oscillating signal 408 is substantially a sinusoidwith a characteristic frequency f₁, and a constant amplitude. FIGS. 5Cand 5F illustrate the first oscillating signal 408 for convenience.

In step 502, for AM, the amplitude of first oscillating signal 408 (FIG.5C) is varied as a function of modulating baseband signal 508 a,resulting in AM modulated signal 510 a (FIG. 5D). Step 502 correspondsto step 404 in the flowchart 400 of FIG. 4A. Another way of describingAM modulation is that the amplitude of modulating baseband signal 508 ais impressed on the amplitude of first oscillating signal 408. Likewisefor ASK, the amplitude of the modulating baseband signal 508 b isimpressed on the amplitude of the first oscillating signal 408,resulting in ASK modulated signal 510 b (FIG. 5G).

The difference between analog AM and ASK is seen by comparing FIG. 5D toFIG. 5G. The analog AM modulated signal 510 a (FIG. 5D) has a smoothlyvarying amplitude “envelope”. In contrast, the amplitude of the ASKmodulated signal 510 b shifts between two discrete levels. Furthermore,based on the forgoing discussions and illustrations, those skilled inthe art(s) will recognize that the present invention can be implementedusing all versions of AM.

4.2.1.2.1.1.2 Structural Description

FIG. 5H illustrates an embodiment of the first stage modulator 420 ingreater detail. In the embodiment of FIG. 5H, the first stage modulator420 is an amplitude modulator 512, which implements either AM orspecifically ASK modulation.

For AM, the modulating baseband signal 308 is an analog modulatingbaseband signal 508 a. The AM modulator 512 accepts the modulatingbaseband signal 508 a and the first oscillating signal 408. The AMmodulator 512 varies the amplitude of the first oscillating signal 408as function of the modulating baseband signal 508 a, resulting in themodulated signal 510 a.

For ASK modulation, the modulating baseband signal 308 is a digitalmodulating baseband signal 508 b. The AM modulator 512 accepts themodulating baseband signal 508 b and the first oscillating signal 408.The AM modulator 512 impresses the amplitude of the modulating basebandsignal 508 b on the amplitude of first oscillating signal 408, resultingin modulated signal 510 b. The amplitude of the modulated signal 510 bgenerally exists at discrete levels, as shown in FIG. 5G.

4.2.1.2.1.2 Second Embodiment: Frequency Modulation Mode, IncludingFrequency Shift Keying Mode

The following discussion describes a method and system for generatingredundant spectrums using frequency modulation, including frequencyshift keying modulation.

4.2.1.2.1.2.1 Operational Description

FIG. 6A depicts a flowchart 600 constituting an embodiment of theflowchart 400 of FIG. 4A. The embodiment depicted by flowchart 600illustrates frequency modulation (FM), which includes frequency shiftkeying modulation(FSK). In the following discussion, the steps inflowchart 600 will be discussed in relation to the example signaldiagrams shown in FIGS. 6B-6G. FIGS. 6B-6D illustrate FM modulation, andFIGS. 6E-6G illustrate FSK modulation.

In step 302, modulating baseband signal 308 is accepted. Modulatingbaseband signal 308 has been previously described as being either ananalog or digital signal. For FM, modulating baseband signal 308 is ananalog signal that is illustrated by analog modulating baseband signal608 a in FIG. 6B. For FSK modulation, modulating baseband signal 308 isa digital signal, which is illustrated by modulating baseband signal 608b in FIG. 6E.

In step 402, first oscillating signal 408 is generated. As discussedpreviously, first oscillating signal 408 is substantially a sinusoidwith characteristic frequency f₁. FIGS. 6C and 6F illustrate firstoscillating signal 408 for convenience.

In step 602 for FM, the frequency of first oscillating signal 408 (FIG.6C) is varied as a function of the modulating baseband signal 608 a,resulting in a FM modulated signal 610 a (FIG. 6D). By comparing FIG. 6Band FIG. 6D, it can be seen that the frequency of FM modulated signal610 a has been varied as a function of the modulating baseband signal608 a.

FSK operates in step 602 in a similar fashion to the FM exampledescribed above except that the input modulating baseband signal 608 bis a digital signal with discrete logic states. As such, FM modulatedsignal 610 b exists at substantially discrete frequency states.

4.2.1.2.1.2.2 Structural Description

FIG. 6H illustrates first stage modulator 420 as an FM modulator 612,which implements FM, including FSK modulation.

For FM, the modulating baseband signal 308 is an analog modulatingbaseband signal 608 a. FM modulator 612 accepts modulating basebandsignal 608 a and first oscillating signal 408. FM modulator 612 variesthe frequency of first oscillating signal 408 as a function of themodulating baseband signal 608 a, resulting in FM modulated signal 610a.

FM modulator 612 operates similarly for FSK modulation, except that themodulating baseband signal 308 is a modulating baseband signal 608 bwith discrete logic states. Thus, the resulting FM modulated signal 610b has discrete frequency states.

4.2.1.2.1.3 Third Embodiment: Phase Modulation, Including Phase ShiftKeying Mode

The following discussion describes a method and system for generatingredundant spectrums using phase modulation, including phase shift keyingmodulation.

4.2.1.2.1.3.1 Operational Description

FIG. 7A depicts a flowchart 700 constituting an embodiment of flowchart400 of FIG. 4A. The embodiment depicted by flowchart 700 illustratesphase modulation (PM), which includes phase shift keying modulation(PSK). In the following discussion, the steps in flowchart 700 will bediscussed in relation to the example signal diagrams shown in FIGS.7B-7H. FIGS. 7B-7D illustrate PM, where modulating baseband signal 308is an analog modulating baseband signal 708 a. FIGS. 7E-7G illustratePSK modulation, where modulating baseband signal 308 is a digitalmodulating baseband signal 708 b.

In step 302, modulating baseband signal 308 is accepted. Modulatingbaseband signal 308 has been previously been described as being eitheran analog or digital signal. For PM, modulating baseband signal 308 isan analog signal, which is illustrated by modulating baseband signal 708a in FIG. 7B. For PSK modulation, modulating baseband signal 308 is adigital signal, which is illustrated by modulating baseband signal 708 bin FIG. 7E.

In step 402, first oscillating signal 408 is generated. As discussedpreviously, first oscillating signal 402 is substantially a sinusoidwith a characteristic frequency f₁. FIGS. 7C and 7F illustrate firstoscillating signal 408 for convenience.

In step 702 for PM, the phase of first oscillating signal 408 (FIG. 7C)is varied as a function of modulating baseband signal 708 a, resultingin an PM modulated signal 710 a (FIG. 7D). FIG. 7D illustrates both PMmodulated signal 710 a, and the first oscillating signal 408 toillustrate the phase shift of PM modulated signal 710 a relative tofirst oscillating signal 408. A comparison of FIG. 7B and FIG. 7D showsthe modulated signal 710 a having a phase shift relative to firstoscillating signal 408 that is a function of modulating baseband signal708 a.

PSK operates in step 702 in a similar fashion to PM, except that theinput modulating baseband signal 708 b is a signal with discrete states.As shown by comparing FIG. 7E to FIG. 7G, in one embodiment, phasemodulated signal 710 b leads the first oscillating signal 408 torepresent a logic “1”, and is in-phase with first oscillating signal 408to represent a logic “0”. Those skilled in the art(s) will recognizethat the amount and direction of phase shift implemented to represent alogic state is completely arbitrary.

4.2.1.2.1.3.2 Structural Description

FIG. 7H illustrates first stage modulator 420 as an PM modulator 712,which implements PM, including PSK modulation.

For PM modulation, PM modulator 712 accepts modulating baseband signal708 a and first oscillating signal 408, where modulating baseband signal708 a is an analog modulating baseband signal. PM modulator 712 shiftsthe phase of first oscillating signal 408 as a function of themodulating baseband signal 708 a, resulting in modulated signal 710 a.

PM modulator 712 operates similarly for PSK modulation, except that themodulating baseband signal 308 is a digital modulating baseband signal708 b with logic states. As such, PM modulator 712 generates a PSKmodulated signal 710 b with a phase that varies in discrete stepsrelative to that of first oscillating signal 408 in order to representthe logic states of modulating baseband signal 308. The amount anddirection of phase shift implemented to represent a logic state iscompletely arbitrary.

4.2.1.2.1.4 Other Embodiments

The embodiments described above for first stage modulator 420 areprovided for purposes of illustration. These embodiments are notintended to limit the invention. Alternate embodiments, differingslightly or substantially from those described herein, will be apparentto persons skilled in the relevant art(s) based on the teachingscontained herein. Such alternate embodiments include combinations of theembodiments described above. Such alternate embodiments fall within thescope and spirit of the present invention.

5 4.2.1.2.2 Second Stage Modulator (Replicator Modulator)

Example embodiments of step 406 in flowchart 400 (FIG. 4A), andreplicator module 422 (FIG. 4I) will be discussed in the followingsection and subsections. The example embodiments include replicating themodulated spectrum 414 by modulating the modulated signal 412 with asecond oscillating signal to generate redundant spectrums 416 a-n.Preferably, the modulated signal 412 is phase or frequency modulatedwith the second oscillating signal, although other modulation schemescould be used including but not limited to amplitude modulation.

4.2.1.2.2.1 First embodiment: Replicating the Modulated Spectrum byPhase Modulating the Modulated Signal

The following discussion describes a method and system for replicatingmodulated spectrum 414 by phase modulating corresponding modulatedsignal 412 to generate redundant spectrums 416 a-n with substantiallythe same information content.

4.2.1.2.2.1.1 Operational Description

FIG. 8A depicts a flowchart 800 which illustrates in greater detail thestep 406 in flowchart 400. Step 406 generates multiple redundantspectrums 416 a-n with substantially the same information content byreplicating modulated spectrum 414. In the following discussion, thesteps in flowchart 800 will be discussed in relation to the examplesignal diagrams shown in FIGS. 8B-8E.

In step 404, the first oscillating signal 408 is modulated with themodulating baseband signal 308 to generate the modulated signal 412 withcorresponding modulated spectrum 414 (FIG. 8B). Modulated spectrum 414includes the necessary amplitude, phase, and frequency information toreconstruct modulating baseband signal 308. This step was discussedearlier, but is repeated here for convenience.

It should be remembered that the frequency spectrum of an EM signalcomprises the relative amplitude and phase information of the frequencycomponents that constitute the EM signal. The time domain representationof an EM signal can be constructed by generating a plurality of sinewaves, that implement the relative amplitude and phase contained in thefrequency spectrum of the EM signal. As such, a given EM signal isuniquely identified by either its time-domain representation or itsfrequency spectrum.

In step 802, a second oscillating signal 806 (FIG. 8C) with acharacteristic frequency f₂ is generated. Second oscillating signal 806is substantially periodic, with a period 808 equal to 1/f₂.

FIG. 8C illustrates without limitation two exemplary waveforms forsecond oscillating signal 806. These waveforms being sinusoid 806 a andsquare wave 806 b, both of which are periodic with frequency f₂. Thoseskilled in the art will recognize there are other types of periodicsecond oscillating signals that could be alternatively used to implementsecond oscillating signal 806, including but not limited to sinusoids,square waves, triangle waves, and arbitrary waveforms with a periodequal to 1/f₂.

Second oscillating signal 806 has corresponding second oscillatingsignal spectrum 810 that is centered about f₂, and is depicted in FIG.8D. Second oscillating signal spectrum 810 has a generic shape that isshown for illustration purposes only, and is not intended to limitsecond oscillating signal 806 in any way. Those skilled in the art willrecognize that the actual shape of spectrum 810 is dependent on thespecific implementation of second oscillating signal 806.

FIG. 8D also illustrates modulating baseband signal spectrum 310 thatcorresponds to modulating baseband signal 308, and modulated spectrum414 that corresponds to modulated signal 412 (FIG. 4F). It will berecalled that modulated signal 412 was generated by modulating firstoscillating signal 408 with modulating baseband signal 308 in step 404of FIG. 4A. Preferably, second oscillating signal spectrum 810 exists ata substantially higher frequency than modulating baseband signalspectrum 310, which is represented by break 809 in the frequency axis ofFIG. 8D. Also typically, modulated spectrum 414 exists at asubstantially higher frequency than second oscillating signal spectrum810, which is represented by break 811 in the frequency axis of FIG. 8E.For example and without limitation, spectrum 310 may have a bandwidth Bon the order of 10 KHZ. Whereas, second oscillating signal spectrum 810may have a center frequency f₂ on the order of 1 MHZ for this example,and modulated spectrum 414 may have a center frequency f₁ on the orderof 100 MHZ for this example.

In step 804, modulated signal 412 (having spectrum 414) is phasemodulated with second oscillating signal 806 (having spectrum 810),resulting in redundant spectrums 812 a-n (FIG. 8E). The effect of phasemodulating modulated signal 412 with a periodic second oscillatingsignal is to shift the phase of modulated signal 412 at the periodicrate f₂ of the second oscillating signal.

FIGS. 8F-8H illustrate phase modulation of a modulated signal 814 by asecond oscillating signal 816, resulting in signal 818. Modulated signal814 is an example of modulated signal 414, and second oscillating signal816 is an example of second oscillating signal 806. As shown, signal 818is shifted by 180 degrees relative to modulated signal 814 at eachtransition of second oscillating signal 816. The phase shift of 180degrees was chosen for convenience of illustration only. Other phaseshifts could be alternatively be used. In one embodiment, for example,the amount of phase shift is on the order of 10 degrees.

FIGS. 8F-8H are shown to illustrate the effect of phase modulation onmodulated signal 814. But for ease of illustration, FIGS. 8F-8G are notdrawn to proper scale. For example and without limitation, modulatedsignal 814 is shown to have a approximately 5 cycles of period 815 torepresent a logic state. Typically, on the order of 10,000 cycles wouldbe used. Furthermore, modulated signal 814 is illustrated to have aperiod 815 that is approximately 1/5 the period 817 of secondoscillating signal 816, which would result in a modulated signal 814 tosecond oscillating signal 816 frequency ratio of 5:1. A typicalmodulated signal 814 to second oscillating signal 816 frequency ratiowould be, for example, on the order to 100:1. Thus, an accuraterepresentation of this numerical example would show 100 periods ofmodulated signal 814 within second oscillating signal period 816. Thisis not shown to ease illustration.

Referring to FIG. 8E, each redundant spectrum 812 a-n carriessubstantially identical information to that in modulated spectrum 414.As such, each redundant spectrum 812 a-n includes the necessaryamplitude, phase, and frequency information to substantially reconstructthe modulating baseband signal 308. Thus, any one of the redundantspectrums 812 a-d can be used to reconstruct modulating baseband signal308 at the receiver.

As shown in FIG. 8E, redundant spectrum 812 a-n are substantiallycentered around f₁, which is the characteristic frequency of firstoscillating signal 408. Also, each redundant spectrum 812 a-n (exceptfor spectrum 812 c) is offset from f₁ by approximately a multiple of f₂(Hz), where f₂ is the frequency of second oscillating signal 806. Thus,each redundant spectrum 812 a-n is offset from an adjacent redundantspectrum 812 a-n in frequency by approximately f₂ Hz. For example,redundant spectrum 812 c is centered around f₁, and redundant spectrums812 b and 812 d are centered at f₁−f₂ and f₁+f₂, respectively.

As stated earlier, example values for f₁ and f₂ are on the order of 100MHZ and 1 MHZ, respectively. As such, spectrums 812 b-d would be locatedat 99 MHZ, 100 MHz, and 101 MHZ, respectively. Thus, according thisnumerical example, spectrums 812 b-d occupy approximately 3 MHZ ofbandwidth that is centered around 100 MHZ; which can be consideredsufficiently narrowband to use commercially under the rules of theappropriate governmental administrative agency (i.e. the FCC). Thesenumerical examples are given for illustration purposes only, and are notmeant to limit this invention in any way. Those skilled in the art willrecognize that the invention could be operated at other frequenciesbased on the discussion herein. In other words, the those skilled in theart(s) will recognize that the invention could be optimized and/oradjusted as desired to meet specific electromagnetic emission rules orother criteria that may exist.

In step 306, the redundant spectrums 812 a-n are transmitted over acommunications medium. It is expected, but not required, that theredundant spectrums 812 a-n would be generated at a first location andsent to a second location over the communications medium. At the secondlocation, the redundant spectrums would be processed to reconstruct themodulating baseband signal 308. In one embodiment, the communicationsmedium is a wireless communications link.

4.2.1.2.2.1.2 Structural Description

FIG. 8I illustrates a block diagram of the replicator system 422according to one embodiment of the present invention. The replicatorsystem 422 comprises a phase modulator 820 and an second oscillator 822.Preferably, replicator system 422 accepts a modulated signal 412 andgenerates multiple redundant spectrums 812 a-n in the manner shown inoperational flowchart 800. In other words, the replicator system 422 isa structural embodiment for performing the operational steps inflowchart 300. However, it should be understood that the scope andspirit of the present invention includes other structural embodimentsfor performing steps in flowchart 800. The specifics of these otherstructural embodiments will be apparent to persons skilled in therelevant art(s) based on the discussion contain herein. Flowchart 800will re-visited to further illustrate the present invention in view ofthe structural components in replicator 422.

In step 404, first stage modulator 420 (FIG. 4I) modulates firstoscillating signal 408 with the modulating baseband signal 308 togenerate the modulated signal 412 with corresponding modulated spectrum414. Modulated spectrum 414 includes the necessary amplitude, phase, andfrequency information of the frequency to reconstruct modulatingbaseband signal 308. This step was discussed earlier, but is repeatedhere for convenience.

In step 802, second oscillator 822 generates the second oscillatingsignal 806 (FIG. 8C) with a characteristic frequency f₂. Secondoscillating signal 806 is periodic with a period 808 equal to 1/f₂.

In step 804, phase modulator 820 shifts the phase of modulated signal412 as a function of second oscillating signal 806, resulting inredundant spectrums 812 a-n (FIG. 8E).

In step 306, the (optional) medium interface module 320 transmitsredundant spectrums 812 a-n over communications medium 322. It isexpected, but not required, that the redundant spectrums 812 a-n wouldbe generated at a first location and sent to a second location over thecommunications medium. At the second location, the redundant spectrumswould be processed to recover the modulating baseband signal 308. In oneembodiment, the communications medium 322 is a wireless communicationslink.

4.2.1.2.2.2 Second embodiment: Replicating the Modulated Spectrum byFrequency Modulating the Modulated Signal

The following discussion describes a method and system for replicatingmodulated spectrum 414 by frequency modulating corresponding modulatedsignal 412 to generate redundant spectrums 416 a-n with substantiallythe same information content.

4.2.1.2.2.2.1 Operational Description

FIG. 8J depicts a flowchart 824 which illustrates in greater detail thestep 406 in flowchart 400. Step 406 generates multiple redundantspectrums 416 a-n with substantially the same information content byreplicating modulated spectrum 414. In the following discussion, thesteps in flowchart 826 will be discussed in relation to the examplesignal diagrams shown in FIGS. 8B-8E. FIGS. 8B-8E were discussed inrelation to the first embodiment of generating redundant spectrums byphase modulating modulated signal 412, but are also applicable to thepresent embodiment of frequency modulating the modulated signal 412.

In step 404, the first oscillating signal 408 is modulated with themodulating baseband signal 308, resulting in the modulated signal 412with corresponding modulated spectrum 414 (FIG. 8B). This step wasdiscussed earlier in FIG. 4A, but is repeated here for convenience.

In step 802, a second oscillating signal 806 (FIG. 8C) with acharacteristic frequency f₂ is generated. This step was discussedearlier in FIG. 8A, but is repeated here for convenience. Preferably,second oscillating signal 806 is substantially periodic, with a period808 equal to 1/f₂. Also, preferably, f₂ for second oscillating signal issubstantially higher that the highest frequency of baseband spectrum310, but is substantially lower than f₁ for the first oscillating signalas represented in FIG. 8D.

In step 826, modulated signal 412 (having spectrum 414) is frequencymodulated with second oscillating signal 806 (having spectrum 810). Inother words, the frequency of modulated signal 412 is varied as afunction of second oscillating signal 806, resulting in redundantspectrums 812 a-n. Each redundant spectrum 812 a-n includes thenecessary amplitude, phase, and frequency information to reconstructmodulating baseband signal 308. As stated, frequency modulating themodulated signal 412 with the second oscillating signal 806 (step 826)results in redundant spectrums 812 a-n that are substantially similar tothat obtained by phase modulating modulated signal 412 with the secondoscillating signal 806 (step 804 in FIG. 8A).

In step 306, the redundant spectrums 812 a-n are transmitted over acommunications medium. It is expected, but not required, that theredundant spectrums 312 a-n would be generated at a first location andsent to a second location over the communications medium. At the secondlocation, the redundant spectrums would be processed to reconstruct themodulating baseband signal 308. In one embodiment, the communicationsmedium is a wireless communications link.

4.2.1.2.2.2.2 Structural Description

FIG. 8K illustrates a block diagram of the replicator system 422according to one embodiment of the present invention. The replicatorsystem 422 comprises a frequency modulator 830 and an second oscillator828. Preferably, replicator system 422 accepts a modulated signal 412and generates multiple redundant spectrums 812 a-n in the manner shownin operational flowchart 824. In other words, the replicator system 422is a structural embodiment for performing the operational steps inflowchart 824 (FIG. 8J). However, it should be understood that the scopeand spirit of the present invention includes other structuralembodiments for performing steps in flowchart 824. The specifics ofthese other structural embodiments will be apparent to persons skilledin the relevant art(s) based on the discussion contained herein.Flowchart 824 will re-visited to further illustrate the presentinvention in view of the structural components in replicator system 422.

In step 404, modulator 420 (FIG. 4I) modulates the first oscillatingsignal 408 with the modulating baseband signal 308, resulting in themodulated signal 412 with corresponding modulated spectrum 414 (FIG.8B). This step was discussed earlier, but is repeated here forconvenience.

In step 802, second oscillator 828 generates the second oscillatingsignal 806 (FIG. 8C) with a characteristic frequency f₂. Secondoscillating signal 806 is periodic with a period 808 equal to 1/f₂.

In step 826, frequency modulator 830 varies the frequency of modulatedsignal 412 as a function of second oscillating signal 806, resulting inredundant spectrums 812 a-n (FIG. 8E).

In step 306, the (optional) medium interface module 320 transmitsredundant spectrums 812 a-n over communications medium 322. It isexpected, but not required, that the redundant spectrums 812 a-n wouldbe generated at a first location and sent to a second location over thecommunications medium. At the second location, the redundant spectrumswould be processed to recover the modulating baseband signal 308.

4.2.1.2.2.3 Other Embodiments

The embodiments described above for replicating a modulated spectrum togenerate redundant spectrums are provided for purposes of illustration.These embodiments are not intended to limit the invention. Alternateembodiments, differing slightly or substantially from those describedherein, will be apparent to persons skilled in the relevant art(s) basedon the teachings contained herein. Such other embodiments include butare not limited to amplitude modulation, and any other modulationtechnique that can be used to replicate the information in a modulatedspectrum. Such alternate embodiments fall within the scope and spirit ofthe present invention. FIG. 8K-1 illustrates a structural diagram ofgenerator 318 that summarizes the embodiments described in section4.2.1.2.2 and related subsections. FIG. 8K-1 illustrates the replicator422 as a second stage modulator 832 and second oscillator 822. Asdiscussed above, second stage modulator 832 (Replicator 422) ispreferably a phase modulator or a frequency modulator, but an amplitudemodulator could also be used or any other type of modulator (or device)that will generate redundant spectrums.

4.2.1.3 Implementation Examples

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above arepresented in this section (and its subsections). These implementationsare presented herein for purposes of illustration, and not limitation.The invention is not limited to the particular implementation examplesdescribed herein. Alternate implementations (including equivalents,extensions, variations, deviations, etc., of those described herein)will be apparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

4.2.1.3.1 First Stage Modulator 420

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above for firststage modulator 420 (FIG. 4I) are presented in this section (and itssubsections). As discussed earlier, first stage modulator 420 modulatesthe first oscillating signal 408 with modulating baseband signal 308,resulting in modulated signal 412. These implementations are presentedherein for purposes of illustration, and not limitation. The inventionis not limited to the particular implementation examples describedherein. Alternate implementations (including equivalents, extensions,variations, deviations, etc., of those described herein) will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

4.2.1.3.1.1 AM Modulator as a Variable Gain Transistor Amplifier

FIG. 9 illustrates an AM modulator 900, which is an example circuitimplementation of AM modulator 512 (FIG. 5H). As discussed earlier, AMmodulator 512 accepts a modulating baseband signal 308 (508 a or 508 b),and a first oscillating signal 408. AM modulator 512 varies theamplitude of the first oscillating signal 408 as a function ofmodulating baseband signal 308, resulting in the modulated signal 412(510 a or 510 b). AM modulator 900 includes: resistors 902, 904, 906,910, and 914; transistor 908; capacitors 903, 912, and 916.

AM modulator 900 operates as a variable gain amplifier, where the gainis a function of the modulating baseband signal 308, and operates asfollows. Transistor 908 operates to amplify the first oscillating signal408. The amount of amplification (or gain) is variable and dependent onthe bias current 909, as is well known to those skilled in the art(s).Bias current 909 is determined by the modulating baseband signal 308 andbias resistors 902, 904, 906, and 910. This occurs because themodulating baseband signal 308 operates as the voltage supply fortransistor 908, and resistors 902, 904, 906, and 910 set the DC biascurrent 909 for a given value of the modulating baseband signal 308, asis well known to those skilled in the art(s). As such, bias current 909varies as a function of the modulating baseband signal 308, as does thegain of transistor amplifier 902. This results in a modulated signal 412(modulated signal 510 a or 510 b) with an amplitude that varies as afunction of modulating baseband signal 308. Capacitors 903 and 916 areDC blocking capacitors. Capacitor 912 and resistor 914 improve the ACgain that is feasible with amplifier 900, as is well known to thoseskilled in the art(s).

AM modulator 900 described above is provided for illustration purposesonly, and is not meant to limit the present invention in any way.Alternate implementations for an AM modulator, differing slightly orsubstantially from that described herein, will be apparent to thoseskilled in the relevant art(s) based on the teachings herein. Suchalternate implementations include, but are not limited to a transistoroscillator configuration, where the output signal amplitude is varied asa function of supply voltage similar to that described above. Suchalternate implementations fall within the scope and spirit of thepresent invention.

4.2.1.3.1.2 FM Modulator as a Voltage Controlled Oscillator

FIG. 10 illustrates voltage controlled crystal oscillator (VCXO) 1000,which is one embodiment of FM modulator 612 (FIG. 6H) and firstoscillator 418 (FIG. 4I). VCXO 1000 accomplishes the functions of bothfirst oscillator 418 and FM modulator 612 because VCXO 1000 generatesfirst oscillating signal 408 and frequency modulates the firstoscillating signal 408 in substantially one step, resulting in modulatedsignal 412 (610 a or 610 b). VCXO 1000 includes varactor bias circuit1002, varactor 1004, and crystal oscillator 1006. Crystal oscillator1006 includes crystal 1008 and transistor 1010.

VCXO 1000 operates as follows. The crystal oscillator 1006 oscillates ata free-running (or unloaded) frequency that is based on the selection ofthe crystal 1008. The free running oscillation frequency is preferablyon the order of the first oscillating signal 408 (FIG. 4D), where firstoscillating signal 408 is referenced here for example purposes onlybecause it has been previously identified as a suitable oscillatingsignal to be modulated by the modulating baseband signal 308 (i.e. itsfrequency is high relative to spectrum 310 that is associated with themodulating baseband signal 308), and is not meant to limit the inventionin any way. The varactor 1004 is preferably a reversed biased diode (orother device) whose effective capacitance changes a function of acontrol voltage as shown in FIG. 11D. The effective capacitance of thevaractor 1004 loads the crystal oscillator 1006 and pulls theoscillation frequency of the crystal oscillator 1006 from itsfree-running oscillation frequency. As such, by controlling the varactor1004 with the modulating baseband signal 308, the oscillation frequencyof the crystal oscillator 1006 varies as a function of the modulatingbaseband signal 308. This results in a modulated signal 412 (610 a or610 b) with a frequency that varies as a function of the modulatingbaseband signal 308.

The VCXO 1000 described above is provided for illustration purposesonly, and is not meant to limit the invention in any way. Alternateimplementations, differing slightly or substantially from that describedherein, will be apparent to those skilled in the art(s) based on theteachings herein. Such alternate implementations include, but are notlimited to, voltage controlled oscillators (VCOs) that use other meansbesides a crystal to determine a free-running oscillation frequency.Such alternate implementations fall within the scope and spirit of thepresent invention.

4.2.1.3.1.3 PM Modulator as a Tunable Filter

FIG. 11A illustrates a tunable bandpass filter (BPF) 1100 which is anexample circuit implementation of the PM modulator 712 (FIG. 7H). Asdiscussed earlier, PM modulator 712 accepts the modulating basebandsignal 308 (708 a or 508 b), and the first oscillating signal 408. ThePM modulator 712 changes the phase of the first oscillating signal 408as a function of the modulating baseband signal 308, resulting inmodulated signal 412 (710 a or 710 b). Tunable BPF 1100 includescapacitors 1102, 1104, and a voltage controlled capacitance device 1106.

Tunable BPF 1100 has a variable amplitude and phase response thatchanges as a function of the effective capacitance of the voltagecontrolled capacitance device 1106. FIGS. 11B and 11C illustrate therelative amplitude and phase response vs. frequency for two effectivecapacitance values of voltage controlled capacitor device 1106. As shownin FIG. 11B, the amplitude response shifts from 1108 a to 1108 b as theeffective capacitance of voltage controlled capacitance device 1106changes from a first capacitance to a second capacitance. Likewise, thecorresponding phase response shifts from 1110 a to 1110 b as theeffective capacitance shifts from a first capacitance value to a secondcapacitance value.

Tunable BPF 1100 is used to phase modulate first oscillating signal 408by controlling the voltage controlled capacitance device 1106 with themodulating baseband signal 308. In one embodiment, voltage controlledcapacitance device 1106 includes varactor bias circuit 1112, varactor1116, and capacitor 1114 as illustrated in FIG. 11E. Varactor 1116 is areversed biased varactor diode whose junction capacitance varies as afunction of a control voltage as shown in FIG. 11D. Capacitor 1114 padsor restricts the amount of tuning, and operates as a DC block forvaractor bias circuit 1112. As such, changes in modulating basebandsignal 308 from V₁ to V₂ will cause the effective capacitance ofvaractor 1116 to change from C₁ to C₂, which will cause the phaseresponse of BPF 1100 to shift from 1110 a to 1110 b. If firstoscillating signal 408 has a corresponding frequency at f₁ the change inmodulating baseband signal 308 from V₁ to V₂ will cause a phase shift ofapproximately 45 degrees as illustrated. The phase shift occurs becausethe phase response of the tunable filter 1100 has shifted from the 1110a to the 1110 b, but the frequency of the first oscillating signal 408is still at f₁. The 45 degree phase shift is meant for example only, andis not meant to limit the invention in any way. Those skilled in the artwill recognize that other values of phase shift can be achieved based onthe discussion given herein.

The present invention is not limited to the bandpass filterconfiguration illustrated by BPF 1100. Those skilled in the art willrecognize that other bandpass filter configurations could be used toimplement phase modulator 712. Furthermore, the present invention is notlimited to tunable bandpass filters to implement phase modulator 712.Those skilled in the art will recognize that other filter configurationscould be used including but not limited to: tunable low pass filters andtunable high pass filters. Also, the present invention is not limited tofilter configurations. Those skilled in the art will recognize thatother circuit configurations can be used to implement the PM modulator712, as long as they shift the phase of first oscillating signal 408 asa function of modulating baseband signal 308.

4.2.1.3.1.4 Other Implementations

The implementations described above for first stage modulator 420 areprovided for purposes of illustration. These implementations are notintended to limit the invention. Alternate implementations, differingslightly or substantially from those described herein, will be apparentto persons skilled in the relevant art(s) based on the teachingscontained herein. Such alternate implementations fall within the scopeand spirit of the present invention.

4.2.1.3.2 Second Stage Modulator

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above for secondstage modulator (Replicator) 422 (FIG. 4I) are presented in this section(and its subsections). These implementations are presented herein forpurposes of illustration, and not limitation. The invention is notlimited to the particular implementation examples described herein.Alternate implementations (including equivalents, extensions,variations, deviations, etc., of those described herein) will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

4.2.1.3.2.1 PM Modulator as a Tunable Filter

FIG. 12A illustrates a tunable bandpass filter (BPF) 1200 which is anexample circuit implementation of PM modulator 820 (FIG. 8I), which isan example embodiment of replicator 422. As discussed earlier, PMmodulator 820 accepts the modulated signal 412 and second oscillatingsignal 806. The PM modulator 820 phase modulates modulated signal 412with second oscillating signal 806. In other words, the PM modulator 820shifts the phase of modulated signal 412 as a function of secondoscillating signal 806, resulting in redundant spectrums 812 a-n.Tunable BPF 1200 includes capacitors 1202, 1204, and voltage controlledcapacitor device 1206.

Tunable BPF 1200 has a variable amplitude and phase response thatchanges as a function of voltage controlled capacitance device 1206.FIGS. 12B and 12C illustrate the relative amplitude and phase responsevs. frequency for two effective capacitance values of voltage controlledcapacitance device 1206. As shown in FIG. 12B, the amplitude responseshifts from 1208 a to 1208 b as the effective capacitance of the voltagecontrolled capacitance device 1206 changes from a first capacitancevalue to a second capacitance value. Likewise, the corresponding phaseresponse shifts from 1210 a to 1210 b as the effective capacitanceshifts from a first capacitance value to a second capacitance value.

Tunable BPF 1200 is used to phase modulate modulated signal 412 withsecond oscillating signal 806 by controlling voltage controlledcapacitance device 1206 with the second oscillating signal 806. In oneembodiment, voltage controlled capacitance device 1206 includes varactorbias circuit 1212, varactor 1216, and capacitor 1214 as is illustratedin FIG. 12E. Varactor 1216 is a reversed biased varactor diode whosejunction capacitance varies as a function of a control voltage, as seenin FIG. 12D. Capacitor 1214 pads or restricts the tuning of theeffective capacitance of voltage controlled capacitance device 1206, andalso operates as a DC block for varactor bias circuit 1212. As such,changes in second oscillating signal 806 from V₁ to V₂ will cause thecapacitance of varactor 1216 to change from C₁ to C₂, which will causethe phase response of BPF 1200 to shift from 1210 a to 1210 b. Ifmodulated signal 412 is centered at f₁, the change in second oscillatingsignal 806 from V₁ to V₂ will cause a phase shift of approximately 45degrees in modulated signal 412, as illustrated. The phase shift occursbecause the phase response of the tunable filter 1200 has shifted fromthe phase response 1210 a to phase response 1210 b, but the frequency ofmodulated signal 412 is still at f₁. The 45 degree phase shift is meantfor example only, and is not meant to limit the invention in any way.Those skilled in the art will recognize that other values of phase shiftcan be achieved based on the discussion given herein.

The present invention is not limited to the bandpass filterconfiguration illustrated by BPF 1200. Those skilled in the art willrecognize that other bandpass filter configurations could be used toimplement phase modulator 820. Furthermore, the present invention is notlimited to tunable bandpass filters to implement phase modulator 820.Those skilled in the art will recognize that other filter configurationscould be used including but not limited to: tunable low pass filters andtunable high pass filters. Also, the present invention is not limited tofilter configurations. Those skilled in the art will recognize thatother circuit configurations can be used to implement phase modulator820, as long as they shift the phase of modulated signal 412 as afunction of second oscillating signal 806.

4.2.1.3.2.2 Other Implementations for a PM Modulator

The implementations described above for PM modulator 820 are providedfor purposes of illustration. These implementations are not intended tolimit the invention. Alternate implementations, differing slightly orsubstantially from those described herein, will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.Such alternate implementations fall within the scope and spirit of thepresent invention.

4.2.1.3.2.3 Implementations for Other Embodiments of Second StageModulator

As discussed above, second stage modulator 422 can also be an FMmodulator (4.2.1.2.2.2), and an AM modulator (Section 4.2.1.2.2.3). Animplementation for an FM modulator and an AM modulator was fullydescribed in sections 4.2.1.3.1.1 and 4.2.1.3.1.2, respectively, towhich the reader is directed for an implementation level description ofthe second stage modulator 422 as an AM modulator and an FM modulator.Furthermore, second stage modulator 422 can be any other type ofmodulator capable of replicating the information in a modulatedspectrum, and the implementation of any such other modulator will beapparent to those skilled in the art(s) based on the discussion herein.

The implementations described above are provided for purposes ofillustration only. These implementations are not intended to limit theinvention. Alternate implementations, differing slightly orsubstantially from those described herein, will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.Such alternate implementations fall within the scope and spirit of thepresent invention.

4.2.2 Generate Redundant Spectrums by Modulating an Oscillating SignalWith a Modulated Signal

The following discussion relates to generating redundant spectrums withsubstantially the same information content by modulating an oscillatingsignal with a modulated signal according to embodiments of the presentinvention.

4.2.2.1 First Embodiment: Generating Redundant Spectrums by PhaseModulating an Oscillating Signal With a Modulated Signal

The following discussion relates to a first embodiment of generatingredundant spectrums by modulating an oscillating signal with a modulatedsignal according to embodiments of the present invention. The firstembodiment includes phase modulating the oscillating signal with amodulated signal to generate redundant spectrums with substantially thesame information content. The second embodiment includes frequencymodulating the oscillating signal with a modulated signal. Otherembodiments are also within the scope and spirit of the invention.

4.2.2.1.1 High Level Description

The following discussion includes an operational process for generatingredundant spectrums by phase modulating an oscillating signal with amodulated signal. Also, a structural description for achieving thisprocess is described herein for illustrative purposes, and is not meantto limit the invention in any way. In particular, the process describedin this section can be achieved using any number of structuralimplementations, at least one of which is described in this section. Thedetails of the structural description will be apparent to those skilledin the art based on the teachings herein.

4.2.2.1.1.1 Operational Description:

FIG. 13A depicts a flowchart 1300 for generating multiple redundantspectrums by phase modulating an oscillating signal with a modulatedsignal. Each redundant spectrum carries the necessary information to atleast substantially or completely reconstruct a modulating basebandsignal. In the following discussion, the steps in FIG. 13A will bediscussed relative to the example signal diagrams shown in FIGS.13B-13K.

In step 302, the modulating baseband signal 308 is accepted. FIG. 13Billustrates the modulating baseband signal 308, and FIG. 13C illustratesa corresponding the spectrum 310 and image spectrum 311 for modulatingbaseband signal 308. It is noted that step 302, signal 308, andspectrums 310, 311 described herein are the same as those described inrelation to FIGS. 3A-3D. They are re-illustrated here for convenience.

In step 1302, a first oscillating signal 1310 (FIG. 13D) is generated.The first oscillating signal 1310 is preferably a sinewave (but otherperiodic waveforms could be used) with a characteristic frequency f₁. Assuch, the first oscillating signal 1310 has a frequency spectrum 1312that is substantially a tone at f₁ (FIG. 13E). Preferably, f₁ for thefirst oscillating signal 408 is much higher than the highest frequency Bin the modulating baseband signal spectrum 310, which is represented bythe break 1311 in the frequency axis of FIG. 13E. For example, thebandwidth B of spectrum 310 is typically on the order of 10 KHz.Whereas, a typical first oscillating signal f₁ will on the order of 100MHZ. These frequency numbers are given for illustration only, and arenot meant to limit the invention in any way.

In step 1304, a second oscillating signal 1314 (FIG. 13F) is generated.The second oscillating signal 1314 is preferable a sinewave (but otherperiodic waveforms could be used) with a constant amplitude andcharacteristic frequency f₂. As such, the second oscillating signal 1314has a frequency spectrum 1316 that is substantially a tone at f₂ (FIG.13G). Preferably, f₂ for the second oscillating signal 1314 issubstantially higher than the highest frequency B in the modulatingbaseband signal spectrum 310, which is represented by the break 1315 inthe frequency axis of FIG. 13G. Also preferably, f₂ is substantiallylower than f₁ for the first oscillating signal 1310; which isrepresented by break 13 11 in the frequency axis of FIG. 13G. Forexample, a typical spectrum 310 has bandwidth B on the order of 10 KHz,and a typical first oscillating signal f₁ is on the order of 100 MHZ.Whereas, a typical second oscillating signal f₂ will be on the order of1 MHZ. These frequency numbers are given for illustration only, and arenot meant to limit the invention in any way.

In step 1306, the second oscillating signal 1314 is modulated with themodulating baseband signal 308, resulting in a modulated (mod) signal1318 (FIG. 13H). The modulated signal 1318 depicts the result ofamplitude modulation (AM), where the amplitude of the modulatingbaseband signal 308 has been impressed on the amplitude of the secondoscillating signal 1314. The use of AM is done for example purposesonly, and is not meant to limit the invention in any way. Any type ofmodulation could be used including but not limited to: amplitudemodulation (AM), frequency modulation (FM), phase modulation (PM), etc.,or any combination thereof. These modulation schemes were described insections 4.2.1.2.1, 4.2.1.2.2, and the reader is referred to the priorsections for additional details.

The modulated signal 1318 has a corresponding modulated spectrum 1320(FIG. 13I) that is centered around f₂, which is the characteristicfrequency of the second oscillating signal 1314. The modulated spectrum1320 carries the necessary amplitude, phase, and frequency informationto reconstruct the modulating baseband signal 308. The modulatedspectrum 1320 is illustrated to have a generic shape and bandwidth.Those skilled in the art will recognize that the actual shape andbandwidth of modulated spectrum 1320 will depend on the specificmodulating baseband signal 308 and type of modulation used to modulatethe second oscillating signal 1314. Furthermore, the modulated spectrum1320 is illustrated to represent double sideband modulation. Thoseskilled in the art will recognize how to implement the present inventionusing single sideband modulation, etc., based on the discussion givenherein.

FIG. 13J illustrates example relative frequency locations of: spectrum310 that corresponds to modulating baseband signal 308; modulatedspectrum 1320 that corresponds to modulated signal 1318, and spectrum1312 that corresponds to first oscillating signal 1310. Typically,modulated spectrum 1320 exists at a substantially higher frequency thanmodulating baseband signal spectrum 310, which is represented by break1315 in the frequency axis. Also, typically, first oscillating signalspectrum 1312 exists at a substantially higher frequency than modulatedspectrum 1320, which is represented by break 1311 in the frequency axisof FIG. 13J. For example, a typical modulating baseband spectrum 310 hasbandwidth B on the order of 10 KHz. Whereas, a typical modulatedspectrum 1320 has a center frequency on the order of 1 MHz, and atypical first oscillating signal spectrum 1312 has a center frequency onthe order of 100 MHZ.

In step 1308, first oscillating signal 1310 is phase modulated withmodulated signal 1318. That is, the phase of the first oscillatingsignal 1310 is shifted as a function of modulated signal 1318, resultingin redundant spectrums 1322 a-n. The degree of phase shift implementedper relative unit change in modulated signal 1318 is completelyarbitrary and is up to the system designer. Each redundant spectrum 1322a-n is substantially identical in information content to the otherredundant spectrums, and carries a copy of the necessary information toreconstruct modulating baseband signal 308. (i.e. each redundantspectrum contains the necessary amplitude, phase, and frequencyinformation to reconstruct the modulating baseband signal 308.)

As shown in FIG. 13K, redundant spectrums 1322 a-n are substantiallycentered around and offset from the first oscillating signal spectrum1312 at f₁; where first oscillating signal 1312 remains substantiallyunmodulated. First oscillating signal spectrum 1312 can be substantiallysuppressed or attenuated in step 1308 by optimizing the amount of phaseshift per unit change in modulated signal 1318 or other phasingtechniques, as is well known to those skilled in the art(s). Also, eachredundant spectrum 1322 a-n is offset from f₁ by approximately amultiple of f₂ (Hz), where f₂ is the frequency of the second oscillatingsignal. Thus, the redundant spectrums 1322 a-n are offset from eachother by f₂ (Hz).

As stated earlier, example values for f₁ and f₂ are on the order of 100MHZ and 1 MHz, respectively. As such, in one example, spectrums 1322 b-eare located at 98 MHZ, 99 MHZ, 101 MHZ, and 102 MHZ, respectively. Thus,according this numerical example, spectrums 1322 b-e occupyapproximately 4 MHZ of bandwidth that is centered around 100 MHZ; whichcan be considered sufficiently narrowband to use commercially under therules of the appropriate governmental administrative agency (i.e. theFCC). These numerical examples are given for illustration purposes only,and are not meant to limit this invention in any way. Those skilled inthe art will recognize that the invention could be operated at otherfrequencies based on the discussion herein. In other words, thoseskilled in the art(s) will recognize that the invention could beoptimized as desired to meet specific electromagnetic emission rulesthat may exist.

In step 306, redundant spectrums 1322 a-n are transmitted over acommunications medium. It is expected, but not required, that theredundant spectrums 1322 a-n would be generated at first location andsent to a second location over the communications medium. At the secondlocation, the redundant spectrums would processed to reconstructmodulating baseband signal 308. In one embodiment, the communicationsmedium is wireless communications link.

As stated above, each redundant spectrum 1322 a-n at least substantiallyor entirely contains a copy of the information necessary to reconstructmodulating baseband signal 308. As such, even if one or more of theredundant spectrums 1322 a-n are corrupted by a jamming signal in thecommunications medium, the modulating baseband signal 308 can still berecovered from any of the other redundant spectrums 1322 a-n that havenot been corrupted.

4.2.2.1.1.2 Structural Description

FIG. 13L illustrates a block diagram of generator 1324 which is oneembodiment of generator 318 according to the present invention.Generator 1324 comprises first oscillator 1330, second oscillator 1326,first stage modulator 1328; and phase modulator 1332. Generator 1324accepts a modulating baseband signal and generates multiple redundantspectrums in the manner shown in operational flowchart 1300. In otherwords, the generator 1324 is a structural embodiment for performing theoperational steps in flowchart 1300. However, it should be understoodthat the scope and spirit of the present invention includes otherstructural embodiments for performing steps in flowchart 1300. Thespecifics of these other structural embodiments will be apparent topersons skilled in the relevant art(s) based on the discussion containedherein. Flowchart 1300 will be re-visited to further illustrate thepresent invention in view of the structural components in generator1324:

In step 302, first stage modulator 1328 accepts the modulating basebandsignal 308.

In step 1302, first oscillator 1330 generates the first oscillatingsignal 1310. Preferably, oscillating signal 1310 is substantially asinusoid (although other periodic waveforms can used) with acharacteristic frequency f₁.

In step 1304, second oscillator 1326 generates second oscillating signal1314. The second oscillating signal 1314 is preferably a sinewave(although other waveforms could be used) with a characteristic frequencyf₂.

In step 1306, the first stage modulator 1328 modulates the secondoscillating signal 1314 with the modulating baseband signal 308,resulting in a modulated (mod) signal 1318, with a correspondingmodulated spectrum 1320 (FIG. 13J) that is centered at f₂. As discussedearlier, first stage modulator 1328 can be any type of modulatorincluding but not limited to: an amplitude modulator, a frequencymodulator, a phase modulator, etc., or a combination thereof.

In step 1308, phase modulator 1332 phase modulates the first oscillatingsignal 1310 with modulated signal 1318. In other words, phase modulator1332 shifts the phase of the first oscillating signal 1310 as a functionof modulated signal 1318, resulting in redundant spectrums 1322 a-n. Thedegree of phase shift per relative unit change in modulated signal 1314is arbitrary, and up to the system designer.

Each redundant spectrum 1332 a-n is substantially identical to the otherredundant spectrums, and carries a copy of the necessary information toreconstruct modulating baseband signal 308. (i.e. each redundantspectrum includes the necessary amplitude, phase, and frequencyinformation to substantially reconstruct the modulating baseband signal308.)

In step 306, (optional) medium interface module 320 (FIG. 3F) transmitsthe redundant spectrums 1322 a-n over a communications medium 322. It isexpected, but not required, that the redundant spectrums 1322 a-n aregenerated at a first location and sent to a second location over thecommunications medium. At the second location, the redundant spectrumsare processed to reconstruct modulating baseband signal 308. In oneembodiment, the communications medium 322 is a wireless communicationslink.

As stated above, each redundant spectrum 1322 a-n at least substantiallyor entirely contains a copy of the information to reconstruct modulatingbaseband signal 308. As such, even if one or more of the redundantspectrums 1322 a-n are corrupted by a jamming signal in thecommunications medium 322, the modulating baseband signal 308 can stillbe recovered from any of the other redundant spectrums 1322 a-n thathave not been corrupted.

4.2.2.1.2 Example Components of the Embodiments

The following section and subsections describe various embodimentsrelated to the method(s) and structure(s) for generating redundantspectrums by phase modulating an oscillating signal with a modulatedsignal. These embodiments are described herein for purposes ofillustration, and not limitation. The invention is not limited to theseembodiments. Alternate embodiments (including equivalents, extensions,variations, deviations, etc., of the embodiments described herein) willbe apparent to persons skilled in the relevant art(s) based of theteachings contained herein. The invention is intended and adapted toinclude such alternate embodiments.

4.2.2.1.2.1 First Stage Modulator

Example embodiments of step 1306 in flowchart 1300 (FIG. 13A), and thefirst stage modulator 1328 are discussed in the following sections. Theexample embodiments include but are not limited to: amplitudemodulation, frequency modulation, phase modulation, and combinationsthereof.

4.2.2.1.2.1.1 First Embodiment: Amplitude Modulation (AM) Mode,Including Amplitude Shift Keying (ASK) Mode

According to an embodiment of the invention, step 1306 includesamplitude modulating the second oscillating signal 1314 with themodulating baseband signal 308. The operational and structuraldescription for such amplitude modulation is substantially similar tothat described in section 4.2.1.2.1.1 above. Specifically, steps 302,402, 502, in flowchart 500 (FIG. 5A) and the related discussion apply toamplitude modulation (AM), which includes amplitude shift keying (ASK).However, in the embodiment being described herein, the secondoscillating signal 1314 replaces first oscillating signal 408 (FIG. 5Cand 5F). Furthermore, the description of AM modulator 512 (FIG. 5H)applies to first stage modulator 1328 when modulator 1328 is an AMmodulator.

4.2.2.1.2.1.2 Second Embodiment: Frequency Modulation (FM) Mode,Including Frequency Shift Keying (FSK) Mode

According to an embodiment of the invention, step 1306 includesfrequency modulating the second oscillating signal 1314 with themodulating baseband signal 308. The operational and structuraldescription for such frequency modulation is substantially similar tothat described in section 4.2.1.2.1.2 above. Specifically, steps 302,402, 602, in flowchart 600 (FIG. 6A) and the related discussion apply tofrequency modulation (FM), which includes frequency shift keying (FSK).However, in the present embodiment being described herein, the secondoscillating signal 1314 replaces first oscillating signal 408 (FIG. 6Cand 6F). Furthermore, the description of FM modulator 612 (FIG. 6H)applies to first stage modulator 1328 when modulator 1328 is an FMmodulator.

4.2.2.1.2.1.3 Third Embodiment: Phase Modulation (PM) Mode, IncludingPhase Shift Keying (PSK) Mode

According to an embodiment of the invention, step 1306 includes phasemodulating the second oscillating signal 1314 with the modulatingbaseband signal 308. The operational and structural description for suchphase modulation is substantially similar to that described in section4.2.1.2.1.3 above. Specifically, steps 302, 402, 702, in flowchart 700(FIG. 7A) and the related discussion apply to phase modulation (PM),including phase shift keying (PSK). However, in the embodiment beingdescribed herein, the second oscillating signal 1314 replaces firstoscillating signal 408 (FIG. 7C and 7F). Furthermore, the description ofPM modulator 712 (FIG. 7H) applies to first stage modulator 1328 whenmodulator 1328 is a PM modulator.

4.2.2.1.2.1.4 Other Embodiments:

The embodiments for the first stage modulator 1328 described above areprovided for purposes of illustration. These embodiments are notintended to limit the invention. Alternate embodiments, differingslightly or substantially from those described herein, will be apparentto those skilled in the relevant art(s) based on the teachings containedherein. Such alternate embodiments include but are not limited tocombinations of the above mentioned embodiments. Such alternateembodiments fall within the scope and spirit of the present invention.

4.2.2.1.3 Implementation Examples

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above arepresented in this section (and its subsections). These implementationsare presented herein for purposes of illustration, and not limitation.The invention is not limited to the particular implementation examplesdescribed herein. Alternate implementations (including equivalents,extensions, variations, deviations, etc., of those described herein)will be apparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

4.2.2.1.3.1 First Stage Modulator 1328

Implementation examples for the first stage modulator 1328 (FIG. 13L)are described below.

4.2.2.1.3.1.1 AM Modulator as a Variable Gain Transistor Amplifier

As described in section 4.2.2.1.2.1.1, the first stage modulator 1328can be an AM modulator. An AM modulator can be implemented as a variablegain transistor amplifier, which is described in detail in section4.2.1.3.1.1 and FIG. 9A, to which the reader is directed for adescription of this aspect of the invention.

4.2.2.1.3.1.2 FM Modulator as a Voltage Controlled Oscillator

As described in section 4.2.2.1.2.1.2, the first stage modulator 1328can be a FM modulator. An FM modulator can be implemented as a voltagecontrolled crystal oscillator (VCXO), which is described in detail insection 4.2.1.3.1.2 and to which the reader is directed for adescription of this aspect of the invention.

4.2.2.1.3.1.3 PM Modulator as a Tunable Filter

As described in section 4.2.2.1.2.1.3, first stage modulator 1328 can bea PM modulator. A PM modulator can be implemented as a tunable filter,which is described in detail in section 4.2.1.3.2.1 and FIGS. 11A-E, towhich the reader is directed for a description of this aspect of theinvention.

4.2.2.1.3.1.4 Other Implementations

The implementations described above for first stage modulator 1328 areprovided for purposes of illustration. These implementations are notintended to limit the invention. Alternate implementations, differingslightly or substantially from those described herein, will be apparentto persons skilled in the relevant art(s) based on the teachingscontained herein. Such alternate implementation include but are notlimited to combinations of the above mentioned implementations. Suchalternate implementations fall within the scope and spirit of thepresent invention.

4.2.2.1.3.2 Phase Modulator 1332

Implementation examples for the phase modulator 1332 (FIG. 13L) aredescribed below.

4.2.2.1.3.2.1. Phase Modulator 1332 as a Tunable Filter

Phase modulator 1332 (FIG. 13L) can be implemented as a tunable filter.The implementation of the phase modulator 1332 as a tunable filter issimilar to the implementation of the phase modulator 820 as a tunablefilter, which was described in detail in section 4.2.1.3.2.1 and FIGS.12A-E. However, for phase modulator 1332 (in contrast to the phasemodulator 820), the modulated signal 1318 controls voltage controlledcapacitance device 1206 (instead of second oscillating signal 806), andfirst oscillating signal 1310 is the input signal to capacitor 1202(instead of modulated signal 412).

4.2.2.1.3.2.2 Other Implementations

The implementation described above for phase modulator 1332 is providedfor purposes of illustration only. These implementation are not intendedto limit the invention. Alternate implementations, differing slightly orsubstantially from those described herein, will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.Such alternate implementations fall within the scope and spirit of thepresent invention.

4.2.2.2 Second Embodiment: Generating Redundant Spectrums by FrequencyModulating an Oscillating Signal With a Modulated Signal

The following discussion relates to a second embodiment of generatingredundant spectrums by modulating an oscillating signal with a modulatedsignal. The second embodiment is to frequency modulate an oscillatingsignal with a modulated signal to generate redundant spectrums withsubstantially the same information content.

4.2.2.2.1 High Level Description

The following discussion includes an operational process for generatingredundant spectrums by frequency modulating an oscillating signal with amodulated signal. Also, a structural description for achieving thisprocess is described herein for illustrative purposes, and is not meantto limit the invention in any way. In particular, the process describedin this section can be achieved using any number of structuralimplementations, at least one of which is described in this section. Thedetails of the structural description will be apparent to those skilledin the art based on the teachings herein.

4.2.2.2.1.1 Operational Description:

FIG. 13M depicts a flowchart 1334 for generating multiple redundantspectrums by frequency modulating an oscillating signal with a modulatedsignal. In the following discussion, the steps in flowchart 1334 will bediscussed in relation to the example signal diagrams shown in FIGS.13B-13K. The signal diagrams illustrated in FIGS. 13B-13K were firstdiscussed in relation to section 4.2.2.1.1.1 (operational description ofgenerating redundant spectrums by phase modulating an oscillatingsignal), but are also applicable to the present embodiment of frequencymodulating an oscillating signal with a modulated signal.

In step 302, the modulating baseband signal 308 is accepted. FIG. 13Billustrates the modulating baseband signal 308, and FIG. 13C illustratesa corresponding the spectrum 310 and image spectrum 311 for modulatingbaseband signal 308. It is noted that step 302, signal 308, andspectrums 310, 311 described herein are the same as those described inrelation to FIGS. 3A-3D. They are re-illustrated here for convenience.

In step 1302, a first oscillating signal 1310 (FIG. 13D) is generated.The first oscillating signal 1310 is preferably a sinewave (but otherperiodic waveforms could be used) with a characteristic frequency f₁. Assuch, the first oscillating signal 1310 has a frequency spectrum 1312that is substantially a tone at f₁ (FIG. 13E). Preferably, f₁ for thefirst oscillating signal 408 is much higher than the highest frequency Bin the modulating baseband signal spectrum 310, which is represented bythe break 1311 in the frequency axis of FIG. 13E. For example, thebandwidth B of spectrum 310 is typically on the order of 10 KHz.Whereas, a typical first oscillating signal f₁ will on the order of 100MHZ. These frequency numbers are given for illustration only, and arenot meant to limit the invention in any way.

In step 1304, a second oscillating signal 1314 (FIG. 13F) is generated.The second oscillating signal 1314 is preferable a sinewave (but otherperiodic waveforms could be used) with a constant amplitude andcharacteristic frequency f₂. As such, the second oscillating signal 1314has a frequency spectrum 1316 that is a tone at f₂ (FIG. 13G).Preferably, f₂ for the second oscillating signal 1314 is substantiallyhigher than the highest frequency B in the modulating baseband signalspectrum 310, which is represented by the break 1315 in the frequencyaxis of FIG. 13E. Also preferably, f₂ is substantially lower than f₁ forthe first oscillating signal 1310; which is represented by break 1311 inthe frequency axis of FIG. 13E. For example, the bandwidth B of spectrum310 is typically on the order of 10 KHz, and f₁ for the firstoscillating signal is typically on the order of 100 MHZ. Whereas, f₂ forthe second oscillating signal is on the order of 1 MHz. These frequencynumbers are given for illustration only, and are not meant to limit theinvention in any way.

In step 1306, the second oscillating signal 1314 is modulated with themodulating baseband signal 308, resulting in a modulated (mod) signal1318 (FIG. 13H). The modulated signal 1318 depicts the result ofamplitude modulation (AM), where the amplitude of the modulatingbaseband signal 308 has been impressed on the amplitude of the secondoscillating signal 1314. The use of AM is done for example purposesonly, and is not meant to limit the invention in any way. Any type ofmodulation scheme could be used including but not limited to: amplitudemodulation (AM), frequency modulation (FM), phase modulation (PM), etc.,or any combination thereof. These modulation schemes were described insections 4.2.1.2.1 3, and the reader is referred to the prior sectionsfor additional details.

The modulated signal 1318 has a corresponding modulated spectrum 1320(FIG. 13I) that is centered around f₂, which is the characteristicfrequency of the second oscillating signal 1314. The modulated spectrum1320 carries the necessary information to reconstruct the modulatingbaseband signal 308. (That is, the modulated spectrum 1320 carries thenecessary amplitude, phase, and frequency information to reconstruct themodulating baseband signal 308.) The modulated spectrum 1320 has ageneric shape and bandwidth. Those skilled in the art will recognizethat the actual shape and bandwidth of modulated spectrum 1320 willdepend on the specific modulating baseband signal 308 and type ofmodulation used to modulate the first oscillating signal 1314.Furthermore, the modulated spectrum 1320 is illustrated to representdouble sideband modulation. Those skilled in the art will recognize howto implement the present invention using single sideband modulation,etc. based on the discussion given herein.

FIG. 13J illustrates the typical relative frequency locations of:spectrum 310 that corresponds to modulating baseband signal 308;modulated spectrum 1320 that corresponds to modulated signal 1318, andspectrum 1312 that corresponds to first oscillating signal 1310.Typically, modulated spectrum 1320 exists at a substantially higherfrequency than modulating baseband signal spectrum 310, which isrepresented by break 1315 in the frequency axis. Also, typically, firstoscillating signal spectrum 1312 exists at a substantially higherfrequency than modulated spectrum 1320, which is represented by break1311 in the frequency axis of FIG. 13J. For example, a typicalmodulating baseband spectrum 310 has bandwidth B on the order of 10 KHz.Whereas, atypical modulated spectrum 1320 has a center frequency on theorder of 1 MHz, and a typical first oscillating signal spectrum 1312 hasa center frequency on the order of 100 MHZ. These frequency values areprovided for illustrative purposes only, and are not limiting. Theinvention can work with any frequency values.

In step 1336, first oscillating signal 1310 is frequency modulated withmodulated signal 1318. That is, the frequency of the first oscillatingsignal 1310 is varied as a function of modulated signal 1318, resultingin redundant spectrums 1322 a-n (FIG. 13K). The amount of frequencyshift implemented per relative unit change in modulated signal 1318 isarbitrary and is up to the system designer. Each redundant spectrum 1322a-n independently includes the necessary amplitude, phase, and frequencyinformation to reconstruct modulating baseband signal 308.

As shown in FIG. 13K, redundant spectrums 1322 a-n are substantiallycentered around and offset from the first oscillating signal spectrum1312 at f₁; where first oscillating signal 1312 remains substantiallyunmodulated. First oscillating signal spectrum 1312 can be substantiallysuppressed or attenuated in step 1308 by optimizing the amount offrequency shift per unit change in modulated signal 1318 or otherfrequency/phasing shifting techniques, as is well known to those skilledin the art(s). Also, each redundant spectrum 1322 a-n is offset from f₁by approximately a multiple of f₂ (Hz), where f₂ is the frequency of thesecond oscillating signal. Thus, each redundant spectrum 1332 a-n isoffset from each other by f₂ (Hz).

As stated earlier, example values for f₁ and f₂ are on the order of 100MHZ and 1 MHz, respectively. As such, in one example, spectrums 1322 b-eare located at 98 MHZ, 99 MHZ, 101 MHZ, and 102 MHZ, respectively. Assuch, according this numerical example, spectrums 1322 b-e occupy abandwidth of approximately 4 MHZ that is centered around 100 MHZ; whichcan be sufficiently narrowband to use commercially under the rules ofthe appropriate governmental or administrative agency (i.e. the FCC orthe equivalent thereof). These numerical examples are given forillustration purposes only, and are not meant to limit this invention inany way. Those skilled in the art will recognize that the inventioncould be operated at other frequencies based on the discussion herein.

In step 306, redundant spectrums 1322 a-d are transmitted over acommunications medium. It is expected, but not required, that theredundant spectrums 1322 a-n would be generated at first location andsent to a second location over the communications medium. At the secondlocation, the redundant spectrums would be processed to reconstructmodulating baseband signal 308. In one embodiment, the communicationsmedium is a wireless communications link.

As stated above, each redundant spectrum 1322 a-n at least substantiallyor entirely contains a copy of the information in spectrum 310. As such,even if one or more of the redundant spectrums 1322 a-n are corrupted bya jamming signal in the communications medium, the modulating basebandsignal 308 can still be recovered from any of the other redundantspectrums 1322 a-n that have not been corrupted.

4.2.2.2.1.2 Structural Description

FIG. 13N illustrates a block diagram of generator 1338, which is oneembodiment of generator 318 according to the present invention.Generator 1338 comprises first oscillator 1330, second oscillator 1326,first stage modulator 1328, and frequency modulator 1340. Generator 1338accepts a modulating baseband signal 308 and generates multipleredundant spectrums 1322 a-n in the manner shown in operationalflowchart 1334. In other words, the generator 1338 is a structuralembodiment for performing the operational steps in flowchart 1334 (FIG.13M). However, it should be understood that the scope and spirit of thepresent invention includes other structural embodiments for performingsteps in flowchart 1334. The specifics of these other structuralembodiments will be apparent to persons skilled in the relevant art(s)based on the discussion contained herein. Flowchart 1334 will bere-visited to further illustrate the present invention in view of thestructural components in generator 1338.

In step 302, first stage modulator 1328 accepts the modulating basebandsignal 308.

In step 1302, first oscillator 1330 generates the first oscillatingsignal 1310. Preferably, first oscillating signal 1310 is substantiallya sinusoid (although other periodic waveforms can used) with acharacteristic frequency f₁.

In step 1304, second oscillator 1326 generates second oscillating signal1314. The second oscillating signal 1314 is preferably a sinewave(although other waveforms could be used) with a characteristic frequencyf₂.

In step 1306, the first stage modulator 1328 modulates the secondoscillating signal 1314 with the modulating baseband signal 308,resulting in a modulated (mod) signal 1318, with a correspondingmodulated spectrum 1320 that is centered at f₂. As discussed earlier,first stage modulator 1328 can be any type of modulator including butnot limited to: an amplitude modulator, a frequency modulator, a phasemodulator, etc., or a combination thereof.

In step 1336, frequency modulator 1338 frequency modulates the firstoscillating signal 1310 with modulated signal 1318. In other words,frequency modulator 1338 shifts the phase of the first oscillatingsignal 1310 as a function of modulated signal 1318, resulting inredundant spectrums 1322 a-n. The degree of phase shift per relativeunit change in modulated signal 1318 is arbitrary, and up to the systemdesigner.

Each redundant spectrum 1332 a-n includes a copy of the necessaryinformation to reconstruct the modulating baseband signal 308. That is,each redundant spectrum contains the necessary amplitude, phase, andfrequency information to reconstruct the modulating baseband signal 308.

In step 306, (optional) medium interface module 320 (FIG. 3F) transmitsthe redundant spectrums 1322 a-n over a communications medium 322. It isexpected, but not required, that the redundant spectrums 1322 a-n aregenerated at a first location and sent to a second location over thecommunications medium. At the second location, the redundant spectrumsare processed to reconstruct the modulating baseband signal 308. In oneembodiment, the communications medium 322 is a wireless communicationslink.

As stated above, each redundant spectrum 1322 a-n at least substantiallyor entirely contains a copy of the information necessary to reconstructthe modulating baseband signal 308. As such, even if one or more of theredundant spectrums 1322 a-n are corrupted by a jamming signal in thecommunications medium 322, the modulating baseband signal 308 can stillbe recovered from any of the other redundant spectrums 1322 a-n thathave not been corrupted.

4.2.2.2.2 Example Component(s) of the Embodiment(s)

The following section and subsections describe various embodimentsrelated to the method(s) and structure(s) for generating redundantspectrums by frequency modulating an oscillating signal with a modulatedsignal. These embodiments are described herein for purposes ofillustration, and not limitation. The invention is not limited to theseembodiments. Alternate embodiments (including equivalents, extensions,variations, deviations, etc., of the embodiments described herein) willbe apparent to persons skilled in the relevant art(s) based of theteachings contained herein. The invention is intended and adapted toinclude such alternate embodiments.

4.2.2.2.2.1 First Stage Modulator

Example embodiments of step 1306 in flowchart 1334 (FIG. 13M), and thefirst stage modulator 1328 include but are not limited to the use of:amplitude modulation, frequency modulation, phase modulation, and othertypes of modulation. These embodiments were discussed in sections4.2.2.1.2.1.1, 4.2.2.1.2.1.2, 4.2.2.1.2.1.3, 4.2.2.1.2.1.4 respectively;to which the reader is directed for a description of this aspect of theinvention. Alternate embodiments, differing slightly or substantiallyfrom those described herein, will be apparent to those skilled in theart(s) based on the discussion given herein. Such alternate embodimentsfall within the scope and spirit of the present invention.

4.2.2.2.3 Implementation Examples

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above arepresented in this section (and its subsections). These implementationsare presented herein for purposes of illustration, and not limitation.The invention is not limited to the particular implementation examplesdescribed herein. Alternate implementations (including equivalents,extensions, variations, deviations, etc., of those described herein)will be apparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

4.2.2.2.3.1 First Stage Modulator 1328

Implementation examples for the first stage modulator 1328 (FIG. 13N)are described below.

4.2.2.2.3.1.1 AM Modulator as a Variable Gain Transistor Amplifier

As described in section 4.2.2.2.2.1, the first stage modulator 1328 canbe an AM modulator. An AM modulator can be implemented as a variablegain transistor amplifier, which is described in detail in section4.2.1.3.1.1 and FIG. 9, to which the reader is directed for adescription of this aspect of the invention.

4.2.2.2.3.1.2 FM Modulator as a Voltage Controlled Oscillator

As described in section 4.2.2.2.2.1, the first stage modulator 1328 canbe a FM modulator. An FM modulator can be implemented as a voltagecontrolled crystal oscillator (VCXO), which is described in detail insection 4.2.1.3.1.2 and FIG. 10, to which the reader is directed for adescription of this aspect of the invention.

4.2.2.2.3.1.3 PM Modulator as a Tunable Filter

As described in section 4.2.2.2.2.1., first stage modulator 1328 can bea PM modulator. A PM modulator can be implemented as a tunable filter,which is described in detail in section 4.2.1.3.2.1 and FIGS. 11A-E, towhich the reader is directed for a description of this aspect of theinvention.

4.2.2.2.3.1.4 Other Implementations

The implementations described above for first stage modulator 1328 areprovided for purposes of illustration. These implementations are notintended to limit the invention. Alternate implementations, differingslightly or substantially from those described herein, will be apparentto persons skilled in the relevant art(s) based on the teachingscontained herein. Such alternate implementation include but are notlimited to combinations of the above mentioned implementations. Suchalternate implementations fall within the scope and spirit of thepresent invention.

4.2.2.2.3.2 Frequency Modulator 1340

Implementation examples for frequency modulator 1340 (FIG. 13N) aredescribed below.

4.2.2.2.3.2.1 Frequency Modulator 1340 as a VCXO

Frequency Modulator 1340 (FIG. 13N) can be implemented as a voltagecontrolled crystal oscillator (VCXO). The implementation of frequencymodulator 1340 as a VCXO is similar to the implementation of FMmodulator 612 as a VCXO, which was fully described in section4.2.1.3.1.2, and FIG. 10. Those skilled in the arts will recognize howto implement frequency modulator 1340 as a VCXO based on the discussionin section 4.2.1.3.1.2, and FIG. 10.

4.2.2.2.3.2.2. Other Implementations

The implementation described above for frequency modulator 1340 isprovided for purposes of illustration only. These implementation are notintended to limit the invention. Alternate implementations, differingslightly or substantially from those described herein, will be apparentto persons skilled in the relevant art(s) based on the teachingscontained herein. Such alternate implementations include but are notlimited to voltage controlled oscillators that do not utilize a crystalfor a frequency frequency reference. Such alternate implementations fallwithin the scope and spirit of the present invention.

4.2.2.3 Other Embodiments:

The embodiments described above in sections 4.2.2.1 and 4.2.2.2 (forgenerating redundant spectrums by modulating an oscillating signal witha modulated signal) are provided for purposes of illustration. Theseembodiments are not intended to limit the invention. Alternateembodiments, differing slightly or substantially from those describedabove, will be apparent to those skilled in the arts based on theteachings given herein. Such alternate embodiments include, but are notlimited to: generating redundant spectrums by amplitude modulating anoscillating signal with a modulated signal; and generating redundantspectrums by using any other modulation technique to modulate anoscillating signal with a modulated signal. FIG. 13N-1 illustrates ageneralized structural embodiment to summarize the embodiments describedin section 4.2.2 and the related subsections. FIG. 13N-1 includes asecond stage modulator 1341 that modulates first oscillating signal 1310with a modulated signal 1318. As discussed in sections 4.2.2.1 and4.2.2.2, second stage modulator 1341 is preferably a phase modulator ora frequency modulator, but may also be an amplitude modulator or anyother type of modulator (or device) that will generate redundantspectrums 1322 a-n.

4.2.3 Generating Redundant Spectrums by Modulating a First ModulatedSignal With a Second Modulated Signal

The following discussion relates to modulating a first modulated (firstmod) signal with a second modulated (second mod) signal to generateredundant spectrums with substantially the same information content.This embodiment allows for a single set of redundant spectrums to carrythe necessary information to reconstruct two distinct modulatingbaseband signals.

4.2.3.1 High Level Description

The following discussion includes an operational process for generatingredundant spectrums by modulating a first modulated signal with a secondmodulated signal. Preferably, the first modulated signal is phase orfrequency modulated with the second modulated signal; although othertypes of modulation could be used including but not limited to AMmodulation. Also, a structural description for achieving this process isdescribed herein for illustrative purposes, and is not meant to limitthe invention in any way. In particular, the process described in thissection can be achieved using any number of structural implementations,at least one of which is described in this section. The details of thestructural description will be apparent to those skilled in the artbased on the teachings herein.

4.2.3.1.1 Operational Description:

FIG. 13O depicts a flowchart 1342 for generating multiple redundantspectrums by modulating a first modulated signal with a second modulatedsignal. In the following discussion, the steps in flowchart 1342 will bediscussed in relation to the example signal diagrams shown in FIGS.13P-13V.

In step 1344, a first modulating baseband signal 1360 (FIG. 13P) isaccepted. First modulating baseband signal 1360 is illustrated as adigital signal for example purposes only, and could be an analog signalas is well known to those skilled in the art(s).

In step 1346, a second modulating baseband signal 1366 (FIG. 13S) isaccepted. Second modulating baseband signal 1366 is illustrated as ananalog signal for example purposes only, and could be an digital signalas is will be understood by those skilled in the art(s).

In step 1348, a first oscillating signal 1362 (FIG. 13Q) is generated.The first oscillating signal 1362 is preferably a sine wave (but otherperiodic waveforms could be used) with a characteristic frequency f₁.Preferably, f₁ for the first oscillating signal is much higher than thehighest frequency of the first modulating baseband signal 1360.

In step 1350, a second oscillating signal 1368 (FIG. 13T) is generated.The second oscillating signal 1368 is preferably a sine wave (but otherperiodic waveforms could be used) with a characteristic frequency f₂.Preferably, f₂ for the second oscillating signal 1368 is much higherthan the highest frequency of the second modulating baseband signal1366, but is substantially lower than f₁ for the first oscillatingsignal 1362.

In step 1352, the first oscillating signal 1362 is modulated with thefirst modulating baseband signal 1360, resulting in first modulated(mod) signal 1364 (FIG. 13R). The first modulated signal 1364 depictsthe result of amplitude modulation, where the amplitude of firstmodulating baseband signal 1360 is impressed on the first oscillatingsignal 1362. The illustration of AM is meant for example purposes only,and is not meant to limit the invention in any way. Any type ofmodulation can be implemented including but not limited to: amplitudemodulation (AM), frequency modulation (FM), phase modulation (PM), etc.,or any combination thereof. These various modulation schemes wereexplored in sections: 4.2.1.2.1.1-4.2.1.2.1.3.

In step 1354, the second oscillating signal 1368 is modulated with thesecond modulating baseband signal 1366, resulting in second modulated(mod) signal 1370 (FIG. 13U). The second modulated signal 1370 depictsthe result of amplitude modulation, where the amplitude of secondmodulating baseband signal 1366 is impressed on the second oscillatingsignal 1368. The illustration of AM is meant for example purposes only,and is not meant to limit the invention in any way. Any type ofmodulation can be implemented including but not limited to: amplitudemodulation (AM), frequency modulation (FM), phase modulation (PM), etc.,or any combination thereof. These various modulation schemes wereexplored in sections: 4.2.1.2.1.1-4.2.1.2.1.3.

In step 1356, the first modulated signal 1364 is modulated with thesecond modulated signal 1370, resulting in redundant spectrums 1372 a-n(FIG. 13V). Preferably, the first modulated signal is phase modulated orfrequency modulated with the second modulated signal; although othermodulation techniques could be used including but not limited toamplitude modulation. In other words, preferably, the phase or frequencyof the first modulated signal is varied as a function of the secondmodulated signal.

Each redundant spectrum 1372 a-n includes the necessary amplitude,phase, and frequency information to substantially reconstruct the secondmodulating baseband signal 1366. Furthermore, the amplitude level ofredundant spectrums 1372 a-n will fluctuate (in mass) between discretelevels over time because first modulated signal 1364 is the result of AMmodulation using digital modulating baseband signal 1360. As such, thefluctuating power level of redundant spectrums 1372 a-n carries theinformation to reconstruct modulating baseband signal 1360.

In step 1358, (optional) medium interface module 320 transmits theredundant spectrums 1372 a-n over communications medium 3222. It isexpected but not required that the redundant spectrums 1372 a-n would begenerated at a first location and sent to a second location over thecommunications medium. At the second location, the redundant spectrums1372 a-n would be processed to reconstruct the first modulating basebandsignal 1360 and the second modulating baseband signal 1366. In oneembodiment, the communications medium is a wireless communications link.

4.2.3.1.2 Structural Description

FIG. 13W illustrates a block diagram of generator 1374, which is oneembodiment of generator 318 according to the present invention.Generator 1374 comprises first oscillator 1376, second oscillator 1382,first stage modulator 1378, first stage modulator 1384, and second stagemodulator 1380. Generator 1374 accepts first modulating baseband signal1360, and second modulating baseband signal 1366, and generates multipleredundant spectrums 1372 a-n in the manner shown in operationalflowchart 1342. In other words, the generator 1374 is a structuralembodiment for performing the operational steps in flowchart 1342.However, it should be understood that the scope and spirit of thepresent invention includes other structural embodiments for performingsteps in flowchart 1342. The specifics of these other structuralembodiments will be apparent to persons skilled in the relevant art(s)based on the discussion contained herein. Flowchart 1342 will bere-visited to further illustrate the present invention in view of thestructural components in generator 1374.

In step 1344, the first stage modulator 1378 accepts first modulatingbaseband signal 1360 (FIG. 13P). First modulating baseband signal 1360is illustrated as digital signal for example purposes only, and could bean analog signal as is well known to those skilled in the art(s).

In step 1346, the first stage modulator 1384 accepts second modulatingbaseband signal 1366 (FIG. 13S). The second modulating baseband signal1366 is illustrated as an analog signal for example purposes only, andcould be an digital signal as is well known to those skilled in theart(s).

In step 1348, first stage modulator 1378 generates the first oscillatingsignal 1362 (FIG. 13Q). The first oscillating signal 1362 is preferablya sine wave (but other periodic waveforms could be used) with acharacteristic frequency f₁. Preferably, f₁ for the first oscillatingsignal is much higher than the highest frequency of the first modulatingbaseband signal 1360.

In step 1350, oscillator 1382 generates the second oscillating signal1368 (FIG. 13T). The second oscillating signal 1368 is preferably a sinewave (but other periodic waveforms could be used) with a characteristicfrequency f₂. Preferably, f₂ for the second oscillating signal 1368 ismuch higher than the highest frequency of the second modulating basebandsignal 1366, but is substantially lower than f₁ for the firstoscillating signal 1362.

In step 1352, the first stage modulator 1378 modulates first oscillatingsignal 1362 with the first modulating baseband signal 1360, resulting infirst modulated signal 1364 (FIG. 13R). The first modulated signal 1364depicts the result of amplitude modulation, where the amplitude of firstmodulating baseband signal 1360 is impressed on the first oscillatingsignal 1362. The illustration of AM is meant for example purposes only,and is not meant to limit the invention in any way. Any type ofmodulation can be implemented including but not limited to: amplitudemodulation (AM), frequency modulation (FM), phase modulation (PM), etc.,or any combination thereof. These various modulation schemes wereexplored in sections: 4.2.1.2.1.1-4.2.1.2.1.3.

In step 1354, the first stage modulator 1384 modulates the secondoscillating signal 1368 with the second modulating baseband signal 1366,resulting in second modulated (mod) signal 1370 (FIG. 13U). The secondmodulated signal 1370 depicts the result of amplitude modulation, wherethe amplitude of second modulating baseband signal 1366 is impressed onthe second oscillating signal 1368. The illustration of AM is meant forexample purposes only, and is not meant to limit the invention in anyway. Any type of modulation can be implemented including but not limitedto: amplitude modulation (AM), frequency modulation (FM), phasemodulation (PM), etc., or any combination thereof. These variousmodulation schemes were explored in sections: 4.2.1.2.1.1-4.2.1.2.1.3.

In step 1356, the second stage modulator 1380 modulates first modulatedsignal 1364 with the second modulated signal 1370, resulting inredundant spectrums 1372 a-n (FIG. 13V). Preferably, second stagemodulator 1380 is a phase or frequency modulator; although other typesof modulators could be used including but not limited to an AMmodulator. As such, preferably, second stage modulator 1380 phasemodulates or frequency modulates the first modulated signal 1364 withthe second modulating signal 1370 to generate redundant spectrums 1372a-n.

Each redundant spectrum 1372 a-n includes the necessary amplitude,phase, and frequency information to substantially reconstruct the secondmodulating baseband signal 1366. Furthermore, the amplitude level ofredundant spectrums 1372 a-n will fluctuate (in mass) between discretelevels over time because first modulated signal 1364 is the result of AMmodulation using digital modulating baseband signal 1360. As such, thefluctuating power level of redundant spectrums 1372 a-n carries theinformation to reconstruct modulating baseband signal 1360.

In step 1358, the (optional) medium interface module 320 generatesredundant spectrums 1372 a-n are transmitted over a communicationsmedium. It is expected but not required that the redundant spectrums1372 a-n would be generated at a first location and sent to a secondlocation over the communications medium. At the second location, theredundant spectrums 1372 a-n would be processed to reconstruct the firstmodulating baseband signal 1360 and the second modulating basebandsignal 1366. In one embodiment, the communications medium is a wirelesscommunications link, and the (optional) medium interface module 320 isan antenna.

5.0 Spectrum Processing Prior To Transmission Over a CommunicationsMedium

As discussed, the present invention generates redundant spectrums thathave substantially the same information content; where each redundantspectrum contains the necessary amplitude, phase, and frequencyinformation to reconstruct the modulating baseband signal. It isexpected but not required that the redundant spectrums would begenerated at a first location and transmitted over a communicationsmedium to a second location. The number of redundant spectrums generatedby the present invention is arbitrary and can be unlimited. However, thetypical communications medium will have a physical and/or administrative(i.e. FCC regulations) bandwidth limitation that will restrict thenumber of redundant spectrums that can be practically transmitted overthe communications medium. Also, there may be other reasons to limit thenumber of spectrums to be transmitted. Therefore, preferably, theredundant spectrums are processed prior to transmission over acommunications medium.

5.1 High Level Description

This section (including its subsections) provides a high leveldescription of processing redundant spectrums prior to transmission overa communications medium according to the present invention. Inparticular, an operational description of processing the redundantspectrums is described at a high level. Also, a structuralimplementation is described herein for illustrative purposes only, andis not limiting. In particular, the process described in this sectioncan be achieved using any number of structural implementations, one ofwhich is described in this section. The details of the possiblestructural implementations will be apparent to those skilled in therelevant art(s) based on the teachings herein.

5.1.1 Operational Description

FIG. 14A depicts flowchart 1400 for processing redundant spectrumsaccording to an embodiment of the present invention. The steps inflowchart 1400 will be discussed in relation to the example signaldiagrams in FIGS. 14B-C. It is expected but not required that step 1402would be performed after step 304 and before step 306 of FIG. 3A. Thatis, it is expected that the steps would be performed after the redundantspectrums are generated but before the redundant spectrums are sent overa communications medium. Steps 304 and 306 are included below forconvenience.

In step 302, a modulating baseband signal 308 (FIG. 3B) is accepted withcorresponding spectrum 310 (FIG. 3C).

In step 304, redundant spectrums 312 a-n (FIG. 14B) are generated.Redundant spectrums 312 a-n were first illustrated in FIG. 3E, and arepresented in FIG. 14B for convenience. As discussed earlier, eachredundant spectrum 312 a-n has the necessary amplitude, and phaseinformation to substantially reconstruct modulating baseband signal 308.

In step 1402, redundant spectrums 312 a-n are processed, resulting inspectrums 1404 b-n (FIG. 14C), which are a subset of redundant spectrums312 a-n. That is, there is at least one less redundant spectrum 1404 b-nwhen compared with redundant spectrums 312 a-n. Although FIGS. 14B-Csuggest that only spectrum 312 a was removed, any spectrum or subset ofspectrums 312 a-n could be removed. Preferably, spectrum removal in step1402 is achieved using a filtering operation, which will be described inmore detail in following subsections. The spectrum removal need not becomplete as long as the spectrum energy in the removed spectrum issufficiently attenuated so as to be negligible compared to the remainingspectrums 1404 b-n. Furthermore, the “a-n” designation is used forconvenience only and puts no limitation on the number of spectrums inredundant spectrums 312 a-n. In other words, “n” is a variable.Likewise, the “b-n” designation puts no limitation on the number ofspectrums in 1404 b-n.

In step 306, redundant spectrums 1404 b-n are transmitted over acommunications medium. It is expected, but not required, that redundantspectrums 1404 b-n are generated at a first location and sent to asecond location over the communications medium. At the second location,the redundant spectrums are processed to reconstruct the modulatingbaseband signal 308. In one embodiment, the communications medium is awireless communications link.

5.1.2 Structural Description

FIG. 14D illustrates a block diagram of transmission system 1406.Transmission system 1406 includes: generator 318, spectrum processingmodule 1408, and (optional) medium interface module 320 according to oneembodiment of the present invention. Transmission system 1406 accepts amodulating baseband signal 308 and transmits redundant spectrums 1404b-n in a manner shown in flowchart 1400. In other words, thetransmission system 1406 is a structural embodiment for performing theoperational steps in flowchart 1400. However, it should be understoodthat the scope and spirit of the present invention includes otherstructural embodiments for performing steps in flowchart 1400. Thespecifics of these other structural embodiments will be apparent topersons skilled in the relevant art(s) based on the discussion containherein. Flowchart 1400 will re-visited to further illustrate the presentinvention in view of the structural components in transmission system1406.

In step 302, generator 318 accepts modulating baseband signal 308 (FIG.3B) that has the corresponding spectrum 310 (FIG. 3C).

In step 304, generator 318 generates redundant spectrums 312 a-n (FIG.14B). Redundant spectrums 312 a-n were first illustrated in FIG. 3E, andare presented in FIG. 14B for convenience. As discussed earlier, eachredundant spectrum 312 a-n has the necessary amplitude and phaseinformation to substantially reconstruct modulating baseband signal 308.

In step 1402, spectrum precessing module 1408 processes redundantspectrums 312 a-n, resulting in redundant spectrums 1404 b-n (FIG. 14C),which are a subset of redundant spectrums 312 a-n. That is, preferably,there is at least one less redundant spectrum 1404 b-n than in redundantspectrums 312 a-n (in other embodiments no spectrums are deleted).

In step 306, (optional) medium interface module 320 transmits redundantspectrums 1404 b-n over communications medium 322. It is expected, butnot required, that redundant spectrums 1404 b-n would be generated at afirst location and sent to a second location over communications medium322. At the second location, the redundant spectrums would be processedto reconstruct the modulating baseband signal 308. In one embodiment,the communications medium 322 is a wireless communications link.

5.2 Example Embodiments:

Various embodiments related to the method(s) and structure(s) describedabove are presented in this section (and its subsections). Theseembodiments are described herein for purposes of illustration, and notlimitation. The invention is not limited to these embodiments. Alternateembodiments (including equivalents, extensions, variations, deviations,etc., of the embodiments described herein) will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.The invention is intended and adapted to include such alternateembodiments.

5.2.1 First Embodiment Processing Redundant Spectrums

The following discussion relates to an operational and structuralembodiment for processing redundant spectrums. Redundant spectrums canbe generated in at least two configurations. In one configuration, theredundant spectrums are a continuous (and unbroken) string of redundantspectrums as is illustrated by redundant spectrums 1508 a-n in FIG. 15B.In an alternative configuration, the redundant spectrums are centeredon, and offset from, an unmodulated spectrum (or tone) as is illustratedby spectrums 1602 a-n in FIG. 16A. The processing of both configurationswill be described concurrently in the following discussion. Otherconfigurations may be possible and are within the scope and spirit ofthe present invention.

5.2.1.1 Operational Description

FIG. 15A depicts flowchart 1500 for processing redundant spectrumsaccording to one embodiment of the present invention. As such, flowchart1500 includes an expansion of step 1402 in flowchart 1400. The steps inflowchart 1500 will be discussed in relation to the example signaldiagrams shown in FIG. 15B-D, and the signal diagrams shown in FIGS.16A-D.

In step 304, redundant spectrums are generated. This step was firstdiscussed in FIG. 3A, but is repeated here for convenience. FIG. 15Billustrates redundant spectrums 1508 a-n, which are a continuous andunbroken string of redundant spectrums that are centered at f₁ (Hz), andoffset from f₁ (Hz) by a multiple of f₂ (Hz). An alternativeconfiguration of redundant spectrums is illustrated in FIG. 16A. FIG.16A illustrates redundant spectrums 1602 a-n which are centered on anoscillating signal spectrum 1604, where oscillating signal 1604 issubstantially unmodulated. Other configurations are possible and arewithin the scope and spirit of the present invention. Breaks 1507 and1601 in the frequency axises of FIGS. 15B and 16A indicate thatspectrums 1508 a-n and 1602 a-n are located above baseband frequencies.

In step 1502, a subset of redundant spectrums is selected. FIG. 15Cillustrates subset 1509, which includes spectrums 1508 c,d that arecentered at f₁ and (f₁+f₂), respectively. FIG. 16 illustrates subset1606, which includes spectrums 1602 c,d and oscillating signal spectrum1604. The redundant spectrums selected for the subsets 1509 and 1606 arecompletely arbitrary, and dependent on system design consideration. Inother words, the selection of spectrums 1508 c,d in subset 1509, and theselection of spectrums 1602 c,d in subset 1606 is meant for illustrationpurposes only and not meant to limit the invention in any way. Otherspectrums could have been chosen as is well known to those skilled inthe art(s). Furthermore, the number of redundant spectrums in thesubsets 1509 and 1606 is not limited to two; greater or fewer redundantspectrums could be chosen. However, there may be a practical bandwidthlimitation to the number of redundant spectrums that should be selectedif the subset of spectrums is to be transmitted over a communicationsmedium, as is well known to those skilled in the art(s).

In step 1503, oscillating signal spectrum 1604 is attenuated as shown inFIG. 16C. Step 1503 is only applicable to redundant spectrums thatcontain an unmodulated spectrum, such as oscillating signal spectrum1604 in FIG. 16B. Even when step 1503 is applicable, it is optionalbased on the choice of the system designer. This is indicated by thedotted line representation for step 1503 in flowchart 1500. Step 1503 isoptional because there may be advantages to transmitting an unmodulatedspectrum (or tone) along with the redundant spectrums. One advantagebeing that an unmodulated tone can be used as a frequency reference atthe receiver for coherent detection configurations, as is well known tothose skilled in the art(s).

In step 1504, the subset of redundant spectrums is upconverted to ahigher frequency. FIG. 15D illustrates subset redundant spectrums 1508c,d, and also includes redundant spectrums 1508 a,b,n. Redundantspectrums 1508 a,b,n are included (despite being removed in step 1502)in order to illuminate the bandwidth effects of up-converting a largestring a redundant spectrums, which may not be apparent if only twospectrums were discussed. FIG. 16E illustrates subset redundantspectrums 1608 c,d, and additional spectrums 1608 a,n for similarreasoning. The bandwidth effect of upconverting redundant spectrumsvaries depending on whether the redundant spectrums were generated usingfrequency modulation. It will be shown below that upconverting redundantspectrums that were generated with frequency modulation (hereinafterreferred to as FM-related spectrums) results in upconverted spectrumsthat occupy a larger frequency bandwidth when compared with theup-conversion of non-FM related spectrums.

FIG. 15E illustrates redundant spectrums 1510 a-n, which results fromupconverting spectrums 1508 a-n that are non-FM related. Redundantspectrums 1510 a-n contain substantially the same information asredundant spectrums 1508 a-n, and thus can be used to reconstruct themodulating baseband signal 308. But, redundant spectrums 1510 a-n arelocated at higher frequencies relative to spectrums 1508 a-n, which isrepresented by the relative placement of break 1511 in the frequencyaxises of FIGS. 15D and 15E. FIG. 15F illustrates redundant spectrums1522 a-n, which result from upconverting redundant spectrums 1508 a-nthat are FM related. Redundant spectrums 1522 a-n also containsubstantially the same information as redundant spectrums 1508 a-n, andcan be used to reconstruct the modulating baseband signal 308.

Referring to FIGS. 15E and 15F, the difference between FM relatedspectrums 1522 a-n (FIG. 15F) and non-FM related spectrums 1510 a-n(FIG. 15E) is that the frequency bandwidth occupied by FM relatedspectrums 1522 a-n is larger than that of non-FM related spectrums 1510a-n. This occurs because the frequency spacing between FM relatedspectrums 1522 a-n has increased by the frequency multiplication factor(“m” in FIGS. 15E-F) relative to the frequency spacing of spectrums 1508a-b. This effect does not occur for non-FM related spectrums 1510 a-n,and can be seen by comparing spectrums 1510 a-n (FIG. 15E) to that ofspectrums 1522 a-n (FIG. 15F).

For example, FM-related spectrums 1522 c,d are located at mf₁ (Hz) andmf₁+mf₂ (Hz), respectively. Thus, the frequency spacing between FMrelated spectrums 1522 c,d is mf₂ (Hz) Whereas, non-FM related spectrums1510 c,d are located at mf₁ and mf₁+f₂, respectively, for a frequencyspacing of f₂ (Hz). The overall result is that up-conversion of non-FMrelated spectrums does not increase the bandwidth occupied by theresulting upconverted spectrums. Whereas, the upconversion of FM relatedspectrums increases the bandwidth occupied by the resulting up-convertedspectrums by a factor of “m”, where “m” is the frequency multiplicationfactor implemented by the up-conversion.

The bandwidth spreading effect described above also applies to spectrums1602 a-n that are centered on unmodulated spectrum 1604, shown in FIG.16D. FIG. 16E illustrates redundant spectrums 1608 a-n, which resultfrom upconverting redundant spectrums 1602 a-n that are non-FM related.And, FIG. 16F illustrates redundant spectrums 1610 a-n, which resultfrom upconverting redundant spectrums 1602 a-n that are FM related.

An advantage of upconverting redundant spectrums is that frequencyupconversion facilitates transmission over a communications medium as iswell known to those skilled in the art(s). This particularly so forwireless links, where relative antenna size requirements vary inverselywith frequency of the signal to be transmitted.

In step 1506, redundant spectrums 1510 c,d and/or spectrums 1608 c,d areamplified. Typically this is done to boost signal power prior totransmission over a communications medium.

In step 306, redundant spectrums 1510 c,d and/or spectrums 1608 c,d aretransmitted over a communications medium. An advantage of transmitting asubset of the full set of redundant spectrums is that the channelbandwidth requirements to carry the redundant spectrums is reduced. Thebandwidth reduction can be substantial since the number of redundantspectrums generated in step 304 can be unlimited.

As stated earlier, flowchart 1500 contains an expansion of step 1402 inflowchart 1400. Specifically, steps 1502-1506 are an expansion of step1402. Steps 1502-1506 are all independent and optional steps forprocessing redundant spectrums after generation. As such, one or more ofsteps 1502-1506 can be eliminated, and/or the order of operation of thesteps can be changed.

5.2.1.2 Structural Description

FIG. 15G illustrates a block diagram of spectrum processing module 1520,which is one embodiment of spectrum processing module 1408. Spectrumprocessing module 1520 includes: filter 1512, center frequencysuppressor 1514, multiplier 1516, and amplifier 1518, according to oneembodiment of the present invention. Spectrum processing module 1408 isone structural embodiment for performing the operational steps inflowchart 1500. However, it should be understood that the scope andspirit of the present invention includes other structural embodimentsfor performing steps in flowchart 1500. The specifics of these otherstructural embodiments will be apparent to persons skilled in therelevant art(s) based on the discussion contain herein. Flowchart 1500will re-visited to further illustrate the present invention in view ofthe structural components in the spectrum processing module 1408.

In step 304, generator 318 generates redundant spectrums. FIGS. 15B and16A illustrates two distinct configurations of redundant spectrums whichcan be generated. FIG. 15B illustrates redundant spectrums 1508 a-n thatare a continuous string of redundant spectrums. FIG. 16A illustratesredundant spectrums 1602 a-n that are centered on a substantiallyunmodulated oscillating signal 1604. Other configurations are possibleand are within the scope and spirit of the present invention.

In step 1502, filter 1512 selects a subset of redundant spectrums. Thepassband of filter 1512 determines which redundant spectrums areselected, and the passband is tunable by changing the effectivereactance of one or more of the filter components as was described insection 4.2.1.3.1.3. FIG. 15C illustrates a passband 1509 containingredundant spectrums 1508 c,d. FIG. 16B illustrates a passband 1606containing redundant spectrums 1602 c,d and oscillating signal 1604.FIGS. 15C and 16B suggest that filter 1512 is a bandpass filter.However, those skilled in the art will recognize that high pass filters,low pass filters, or other known filter combinations would be useful forfiltering redundant spectrums to select a subset of redundant spectrums.These other filter configurations are within the scope and spirit of thepresent invention.

In step 1503, center frequency suppressor 1514 attenuates firstoscillating signal spectrum 1604 as shown in FIG. 16C. Center frequencysuppressor 1514 is applicable to redundant spectrums that contain anunmodulated spectrum, such as unmoduilated oscillating signal spectrum1604 in FIG. 16B. Even when center frequency suppressor 1514 isapplicable, it is optional because an unmodulated spectrum (or tone) maybe ignored or used as a frequency reference at the receiver for coherentdetection systems. Center frequency suppressor 1514 is typically abandstop filter that has a stop band 1603 that encompasses oscillatingsignal spectrum 1604, but not the adjacent redundant spectrums 1602 c,d,as is illustrated in FIG. 16C. Other filter configurations may be usefulincluding but not limited to a combination of lowpass and highpassfilter as will be understood by those skilled in the art(s) based on thediscussion given herein. Furthermore, phasing techniques can beimplemented during redundant spectrum generation to attenuate firstoscillating signal spectrum 1604 as was discussed in section4.2.2.1.1.1.

In step 1504, up-converter 1516 upconverts the redundant spectrums to ahigher frequency. FIG. 15E illustrates redundant spectrums 1510 a-nwhich results when redundant spectrums 1508 a-n are non-FM relatedspectrums. FIG. 15F illustrates redundant spectrums 1522 a-n whichresults when redundant spectrums 1508 a-n are FM-related spectrums. Itwill be noted spectrums 1522 a-n occupy a bandwidth larger than that ofspectrums 1508 a-n by a factor of m, where m is the frequencymultiplication factor associated with the up-conversion. Similarly, FIG.16E illustrates redundant spectrums 1608 a-n which results whenspectrums 1602 a-n are non-FM related. FIG. 16F illustrates redundantspectrums 1610 a-n which results when spectrums 1610 a-n are FM related.

Upconverted redundant spectrums 1510 a-n (FIG. 15E) and spectrums 1522a-n are located at frequencies that are a multiple of the frequencylocations of redundant spectrums 1508 a-n. This would suggest thatup-converter 1516 is a frequency multiplier. This is but one embodiment,other up-converters could be used including but not limited to frequencymixers. Frequency mixers are capable of upconverting redundant spectrumsto higher frequencies that are not multiples of the lower frequencies aswill be understood by those skilled in the art(s) based on thediscussion given herein.

In step 1506, amplifier 1518 amplifies redundant spectrums 1510 a,b.Likewise for spectrums 1608 a,b. Typically this is done to boost signalpower prior to transmission over a communications medium.

In step 306, (optional) medium interface module 320 transmits redundantspectrums 1510 a,b and/or spectrums 1608 a,b over the communicationsmedium 322. The effect of selecting a subset of redundant spectrums fortransmission is that the channel bandwidth occupied by the transmittedspectrums is reduced compared with that occupied by the redundantspectrums generated in step 304. The bandwidth reduction can besubstantial since the number of redundant spectrums generated in step304 can be unlimited. Furthermore, the number of redundant spectrums inthe subset can be optimized so the occupied bandwidth will besufficiently narrow that the subset can be used commercially under therules of the appropriate governmental administrative agency (i.e. theFCC).

As discussed, spectrum processing module 1520 is one structuralembodiment for performing the steps 1502-1506 in flowchart 1500. Asstated above, the performance of steps 1502-1506 is optional and/ortheir order of operation can be changed. Therefore, the components inspectrum processing module 1520 are also optional and/or their order canrearranged.

5.2.2. Other Embodiments:

The embodiment described above for processing redundant spectrums isprovided for purposes of illustration. This embodiment is not intendedto limit the invention. Alternate embodiments, differing slightly orsubstantially from that described herein, will be apparent to thoseskilled in the relevant art(s) based on the teachings given herein. Forexample, up-converter 1516 can be designed to up-convert only thosefrequencies containing the spectrums of interest. Alternatively, theamplifier 1518 can be designed to amplify only those frequenciescontaining the spectrums of interest. Such alternate embodiments fallwithin the scope and spirit of the present invention.

5.2.3 Implementation Example(s)

Exemplary operational and/or structural implementations related to themethod(s), structure(s), and/or embodiments described above arepresented in this section (and its subsections). These implementationsare presented herein for purposes of illustration, and not limitation.The invention is not limited to the particular implementation examplesdescribed herein. Alternate implementations (including equivalents,extensions, variations, deviations, etc., of those described herein)will be apparent to persons skilled in the relevant art(s) based on theteachings contained herein. Such alternate implementations fall withinthe scope and spirit of the present invention.

5.2.3.1 Implementation Example(s) for Frequency Up-conversion

This section provides a structural description of frequencyup-conversion system 1620 (FIG. 16G), which is an implementation forup-converter 1516. As discussed above, up-converter 1516 upconvertsredundant spectrums to a higher frequency. The frequency up-conversionsystem 1620 is further described in the copending U.S. patentapplication entitled “Method and System for Frequency Up-conversion”, ofcommon Assignee, Ser. No. 09/17615; which is incorporated herein byreference in its entirety. The following describes frequencyup-conversion of an input signal (e.g. redundant spectrums 1508 c,d),resulting in an output signal (e.g. redundant spectrums 1510 c,d).

Frequency up-conversion system 1620 is illustrated in FIG. 16G. An inputsignal 1622, such as a frequency modulated (FM) input signal 1652 ofFIG. 16L, is accepted by a switch module 1624. It should be noted inFIG. 16L that FM input signal 1652 may have been generated by modulatingoscillating signal 1650 (FIG. 16K) with information signal 1648 (FIG.16J). The embodiment shown in FIG. 16L is for the case wherein theinformation signal 1648 is a digital signal and the frequency ofoscillating signal 1650 is varied as a function of the value ofinformation signal 1648. This embodiment is referred to as frequencyshift keying (FSK) which is a subset of FM. It will be apparent to thoseskilled in the relevant art(s) that information signal 1648 can beanalog, digital, or any combination thereof, and that any modulationscheme can be used. The output of switch module 1624 is a harmonicallyrich signal 1626, shown in FIG. 16M as a harmonically rich signal 1654that has a continuous and periodic waveform. FIG. 16N is an expandedview of two sections of harmonically rich signal 1654 that includessection 1656 and section 1658. This waveform is preferably a rectangularwave, such as a square wave or a pulse (although, the invention is notlimited to this embodiment). For ease of discussion, the term“rectangular waveform” is used to refer to waveforms that aresubstantially rectangular. In a similar manner, the term “square wave”refers to those waveforms that are substantially square and it is notthe intent of the present invention that a perfect square wave begenerated or needed. Harmonically rich signal 1626 is comprised of aplurality of sinusoidal waves whose frequencies are integer multiples ofthe fundamental frequency of the waveform. These sinusoidal waves arereferred to as the harmonics of the underlying waveform, and thefundamental frequency is referred to as the first harmonic. FIG. 16O andFIG. 16P show separately the sinusoidal components making up the first,third, and fifth harmonics of section 1656 and section 1658,respectively. (Note that there are an infinite number of harmonics, and,in this example, because harmonically rich signal 1654 is shown as asquare wave, there will only be odd harmonics.) These three harmonicsare shown simultaneously (but not summed) in FIG. 16Q for section 1656and section 1658. The relative amplitudes of the harmonics are generallya function of the relative widths of the pulse width of harmonicallyrich signal 1626 and the period of the fundamental frequency, and can bedetermined by doing a Fourier analysis of harmonically rich signal 1626.As further described below, according to an embodiment of the invention,the pulse width of input signal 1622 is adjusted to ensure that theamplitude of the desired harmonic is sufficient for its intended use(e.g., transmission). A filter 1628 filters out the undesiredfrequencies (harmonics), and outputs an electromagnetic (EM) signal atthe desired harmonic frequency as an output signal 1630, shown as afiltered output signal 1660 in FIG. 16R. FIG. 16R illustrates that thefifth harmonic of sections 1656 and 1658 where selected by filter 1628.Filter 1628 can be filtered to select other harmonics as will beunderstood by those skilled in the relevant art(s).

Looking at FIG. 16H, switch module 1624 is seen as comprised of a biassignal 1632, a resistor 1634, a switch 1636, and a ground 1638 (oranother voltage reference). The input signal 1622 controls the switch1636, and causes it to close and open. Harmonically rich signal 1626 isgenerated at a point located between the resistor 1634 and the switch1636.

Also in FIG. 16H, it can be seen that filter 1628 is comprised of acapacitor 1640 and an inductor 1642 shunted to a ground 1643. The filteris designed to filter out the undesired harmonics of harmonically richsignal 1626.

In an alternate embodiment, FIG. 16I illustrates an unshaped inputsignal 1644 being routed to a pulse shaping module 1646 to become inputsignal 1622 and then routed to the switch module 1624. Looking to thewaveforms of FIGS. 16J-R, this would have the effect of routing FM inputsignal 1652 into pulse shaping module 1646. The purpose of the pulseshaping module 1646 is to control the pulse width of the input signal1622 controlling the opening and closing of the switch 1636 in switchmodule 104. The pulse width of the input signal 1622 controls theopening and closing of switch 206 to determine the pulse width of theharmonically rich signal 1626. As stated above, a factor in determiningthe relative amplitudes of the harmonics of harmonically rich signal1626 is determined by its pulse width. For example, an efficient pulsewidth would be approximately ½ the period of the desired harmonic thatis output signal 1630. For example, if an output signal of 900 MHZ wasdesired, then the pulse width would be approximately 555 pico-seconds(½·1/900 MHZ).

5.2.3.2 Other Implementation(s)

The implementation for up-converter 1516 described above is for providedfor purposes of illustration. This implementation is not intended tolimit the invention in any way. Alternate implementations, differingslightly or substantially from that described herein, will be apparentto those skilled in the relevant art(s) based on the teachings containedherein. Alternate implementations include but are not limited to variousmixer circuits, various frequency multiplier circuit configurations, andother well known up-converter apparatus. Such alternate implementationsfall within the scope and spirit of the present invention.

6.0 Recovering a Demodulated Baseband Signal From Redundant SpectrumsThat Have Substantially the Same Information Content

6.1 High Level Description

This section (including subsections) provides a high level descriptionof an embodiment of recovering a demodulated baseband signal fromredundant spectrums that were generated with substantially the sameinformation content. The following discussion includes an exemplaryoperational process for recovering a demodulated baseband signal fromredundant spectrums. Also, a structural description for achieving thisprocess is described herein for illustrative purposes, and is not meantto limit the invention in any way. In particular, the process describedin this section can be achieved using any number of structuralimplementations, at least one of which is described in this section. Thedetails of the structural description will be apparent to those skilledin the art based on the teachings herein.

6.1.1 Operational Description:

FIG. 17A depicts flowchart 1700 for recovering a demodulated basebandsignal from redundant spectrums according to one embodiment of thepresent invention. In the following discussion, the steps in FIG. 17Awill be discussed in relation to the example signal diagrams in FIGS.17B-17GH.

In step 306, redundant spectrums 1710 a-c (FIG. 17B) are transmittedover a communications medium from a first location. This step wasdiscussed in FIGS. 3A, 4A, 8A, 13A, 14A, 15A, 16A, and relateddiscussions and is mentioned here for convenience. Each redundantspectrum 1710 a-c carries the necessary information to reconstructmodulating baseband signal 308. In other words, each redundant spectrum1710 a-c includes the necessary amplitude, phase, and frequencyinformation to reconstruct the modulating baseband signal 308.Furthermore, the redundant spectrums 1710 a-c are typically located at afrequency that is substantially higher than the baseband spectrum 310that is associated with the modulating baseband signal 308, asillustrated by break 1709 in the frequency axis. As is the casethroughout this specification, modulating baseband signal 308 can be anytype of arbitrary signal including but not limited to an analog signal,a digital signal, or a combination thereof.

As discussed in earlier, the number of redundant spectrums that aretransmitted over the communications medium is arbitrary. In other words,FIG. 17B depicts redundant spectrums 1710 a-c for illustration purposesonly; greater or fewer redundant spectrums can be transmitted over thecommunications medium. A general limit to the number of redundantspectrums that can be transmitted is the available channel bandwidth.Legal or administrative limits (i.e. FCC regulations) may furtherrestrict the number of redundant spectrums that can be transmitted overa communications medium.

In step 1702, redundant spectrums 1712 a-c are received (FIG. 17C) fromthe communications medium. Redundant spectrums 1712 a-c aresubstantially similar to redundant spectrums 1710 a-c that weretransmitted in step 306, except for changes introduced by thecommunications medium. Such changes can include but are not limited tosignal attenuation, and signal interference. For example, FIG. 17Cdepicts jamming spectrum 1711 existing within the same frequencybandwidth as that occupied by spectrum 1712 b in order to illustrate theadvantages of the present invention. Jamming signal spectrum 1711 is afrequency spectrum associated with a generic jamming signal. Forpurposes of this invention, a “jamming signal” refers to any unwantedsignal, regardless of origin, that may interfere with the properreception and reconstruction of an intended signal. Furthermore, thejamming signal is not limited to tones as depicted by spectrum 1711, andcan have any generic spectral shape, as will be understood by thoseskilled in the art(s).

In step 1704, redundant spectrums 1712 a-c are translated to lowerintermediate frequencies, resulting in redundant spectrums 1714 a-c(FIG. 17D) that are located at intermediate frequencies f_(IFA),f_(IFB), and f_(IFC) respectively, with frequency separationapproximately equal to f₂ (Hz). Redundant spectrums 1714 a-c containsubstantially the same information content as spectrums 1712 a-c, exceptthat they exist at a substantially lower frequency; which is representedby the relative placement of break 1709 in the frequency axis of FIG.17D. Jamming signal spectrum 1711 is also translated to a lowerfrequency since it is located within the bandwidth of spectrum 1712 b,resulting in jamming signal spectrum 1716.

In step 1706, redundant spectrum 1714 a-c are isolated from each otherinto separate channels, resulting in channels 1718 a-c (shown in FIGS.17E-17G). As such, channel 1718 a comprises redundant spectrum 1714 a;channel 1718 b comprises redundant spectrum 1714 b and jamming signalspectrum 1716; and channel 1718 c comprises redundant spectrum 1714 c.Each channel 1718 a-c carries the necessary amplitude, phase, andfrequency information to reconstruct the modulating baseband signal 308because redundant spectrums 1714 a-c carry such information. However,channel 1718 b also carries jamming signal spectrum 1716 that mayprevent channel 1718 b from being used to reconstruct modulatingbaseband signal 308, depending on the relative signal strength ofjamming signal spectrum 1716.

In step 1708, demodulated baseband signal 1720 (FIG. 17H) is extractedfrom channels 1718 a-c; where demodulated baseband signal 1720 issubstantially similar to modulated baseband signal 308.

An advantage of the present invention should now be apparent. Therecovery of modulating baseband signal 308 can be accomplished in spiteof the fact that high strength jamming signal(s) (e.g. jamming signalspectrum 1711) exist “in band” on the communications medium. Theintended baseband signal can be recovered because multiple redundantspectrums are transmitted, where each redundant spectrum carries thenecessary information to reconstruct the baseband signal. At thedestination, the redundant spectrums are isolated from each other sothat the baseband signal can be recovered even if one or more of theredundant spectrums are corrupted by a jamming signal.

6.1.2 Structural Description:

FIG. 17I illustrates an example receiver module 1730. Receiver module1730 includes: (optional) medium interface module 1722, down-converter1724, spectrum isolation module 1726, and signal extraction module 1728.Preferably receiver module 1730 generates demodulated baseband signal1720 from redundant spectrums 1712 a-c. In other words, receiver module1730 is a structural embodiment for performing the operational steps inflowchart 1700. However, it should be understood that the scope andspirit of the of the present invention includes other structuralembodiments for performing the steps of flowchart 1700. Flowchart 1700will be revisited to further illustrate the present invention in view ofthe structural components in receiver module 1730.

In step 306, (optional) medium interface module 320 transmits redundantspectrums 1710 a-c (FIG. 17B) over the communications medium 322 from afirst location. This step was discussed in FIGS. 3A, 4A, 8A, 13A, 14A,15A, 16A, and the related discussions, and is mentioned here forconvenience. Each redundant spectrum 1710 a-c carries the necessaryinformation to reconstruct modulating baseband signal 308. In otherwords, each redundant spectrum 1710 a-c carries the necessary amplitude,phase and frequency information to reconstruct the modulating basebandsignal 308. Furthermore, the redundant spectrums 1710 a-n are typicallylocated at a frequency that is substantially higher than the basebandspectrum 310 that is associated with the modulating baseband signal 308,as illustrated by break 1709 in the frequency axis.

As discussed in earlier, the number of redundant spectrums that aretransmitted over the communications medium is arbitrary. In other words,FIG. 17B depicts redundant spectrums 1710 a-c for illustration purposesonly; greater or fewer redundant spectrums can be transmitted over thecommunications medium. One limit to the number of redundant spectrumsthat can be transmitted is the available channel bandwidth.

In step 1702, (optional) medium interface module 1722 receives redundantspectrums 1712 a-c (FIG. 17C) from the communications medium 322.Redundant spectrums 1712 a-c are substantially similar to redundantspectrums 1710 a-c that were transmitted in step 306, except for changesintroduced by the communications medium. Such changes can include butare not limited to signal attenuation, and signal interference. Forexample, FIG. 17C depicts jamming signal spectrum 1711 existing withinthe same frequency bandwidth as that occupied by spectrum 1712 b inorder to illustrate the advantages of the present invention. Jammingsignal spectrum 1711 is a frequency spectrum associated with a genericjamming signal. For purposes of this invention, a “jamming signal”refers to any unwanted signal, regardless of origin, that may interferewith the proper reception and reconstruction of an intended signal.Furthermore, the jamming signal is not limited to tones, and can haveany generic spectrum shape, as will be understood by those skilled inthe art(s).

In step 1704, down-converter 1724 translates redundant spectrums 1712a-c to a lower frequency; resulting in redundant spectrums 1714 a-c(FIG. 17D) that are located at frequencies f_(IFA), f_(IFB), andf_(IFC), respectively, with frequency separation approximately equal tof₂ (Hz). Redundant spectrums 1714 a-c have substantially the sameinformation content as spectrums 1712 a-c, except that they exist at asubstantially lower frequency; which is represented by the relativeplacement of break 1709 in frequency axis of FIG. 17D. Jamming signalspectrum 1711 is also translated to a lower frequency since it islocated within the bandwidth of spectrum 1712 b, resulting in jammingsignal spectrum 1716.

In step 1706, spectrum isolation module 1726 isolates redundantspectrums 1714 a-c from each other into separate channels, resulting inchannels 1718 a-c (shown in FIGS. 17E-17G). As such, channel 1718 acomprises redundant spectrum 1714 a; channel 1718 b comprises redundantspectrum 1714 b and jamming signal spectrum 1716; and channel 1718 ccomprises redundant spectrum 1714 c. Each channel 1718 a-c carries thenecessary amplitude, phase, and frequency information necessary toreconstruct modulating baseband signal 308 because redundant spectrums1714 a-c carry such information. However, channel 1718 b also carriesjamming signal spectrum 1716 that may prevent channel 1718 b from beingused to reconstruct modulating baseband signal 308, depending on therelative signal strength of jamming signal spectrum 1716.

In step 1708, signal extraction module 1728 recovers demodulatedbaseband signal 1720 from channels 1718 a-c; where demodulated basebandsignal 1720 is substantially similar to modulated baseband signal 308.

An advantage of the present invention should now be apparent. Therecovery of modulating baseband signal 308 can be accomplished in spiteof the fact that high strength jamming signal(s) exist “in band” on thecommunications medium. The intended baseband signal can be recoveredbecause multiple redundant spectrums are transmitted over thecommunications medium, where each redundant spectrum carries thenecessary information to reconstruct the baseband signal. At thedestination, the redundant are isolated from each other so that thebaseband signal can be recovered even if one or more of the redundantspectrums are corrupted Further illustration and discussion will begiven in following sections.

6.2. Example Embodiments

Various embodiments related to the method(s) and structure(s) describedabove are presented in this section (and its subsections). Specifically,the following discussion describes example embodiments of recovering ademodulated baseband signal from multiple redundant spectrums. Theseembodiments are described herein for purposes of illustration, and notlimitation. The invention is not limited to these embodiments. Alternateembodiments (including equivalents, extensions, variations, deviations,etc., of the embodiments described herein) will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.The invention is intended and adapted to include such alternateembodiments.

6.2.1 Down-conversion

Example embodiments of step 1704 and down-converter 1724 will bediscussed as follows. A first embodiment includes translating redundantspectrums to a lower intermediate frequency (IF) by mixing the redundantspectrums with a local oscillating signal at the receiver. A secondembodiment includes down-conversion by aliasing the redundant spectrumsusing a universal frequency translation (UFT) module. Other methods andsystems of down-conversion are also included.

6.2.1.1 Down-conversion by Mixing Redundant Spectrums With anOscillating Signal

The following discussion describes a method and system for translatingredundant spectrums to lower intermediate frequencies (IF) by mixing theredundant spectrums with a local oscillating signal.

6.2.1.1.1 Operational Description:

FIG. 18A depicts flowchart 1800 for translating redundant spectrums to alower frequency (step 1704, FIG. 17A) according to one embodiment of thepresent invention. In the following discussion, the steps in FIG. 18Awill be discussed in relation to the example signal diagrams in FIGS.18B-18H.

In step 1702, redundant spectrums 1712 a-c are received (FIG. 18B) froma communications medium. Step 1702 and spectrums 1712 a-c were firstdiscussed in FIGS. 17A and 17C, respectively, and are repeated here forconvenience.

In step 1802, a local oscillating signal 1806 (FIG. 18C) is generated.The local oscillating signal 1806 is preferably a sine wave (althoughother periodic waveforms can be used) with a characteristic frequencyf₃. The local oscillating signal 1806 has a spectrum 1808 (FIG. 18D)that is preferably a tone, but other spectrums could be useful as iswell known those skilled in the art(s).

In step 1804, redundant spectrums 1712 a-c are mixed with localoscillating signal 1806, resulting in redundant spectrums 1810 a-c (FIG.18E) that are located at intermediate frequencies (f₁−f₂)−f₃, f₁−f₃, and(f₁+f₂)−f₃, respectively. Redundant spectrums 1810 a-c containsubstantially similar information to that of spectrums 1712 a-c, exceptthat they exist at a substantially lower frequency; which is representedby the relative placement of break 1709 in the frequency axis of FIG.18E. Jamming signal spectrum 1711 is also translated to a lowerfrequency since it is located within the bandwidth of spectrum 1712 b,resulting in jamming signal spectrum 1811.

The frequency (f₁−f₃) produced by the mixing f₁ with f₃ (step 1804) isreferred to as the difference frequency by those skilled in the art(s).Typically, the mixing process will also produce spectrums centered at asum frequency (f₁+f₃), which is not shown in FIG. 18E because it isoutside the relevant frequency band defined by break 1709 in thefrequency axis. The spectrums located in and around the sum frequencycan be attenuated or suppressed by a number of methods including but notlimited to filtering, as is will be understood by those skilled in theart(s).

In step 1706, redundant spectrum 1810 a-c are isolated from each otherinto channels 1812 a-c (shown in FIGS. 18F-18H, respectively). As such,channel 1812 a comprises redundant spectrum 1810 a; channel 1812 bcomprises redundant spectrum 1810 b and jamming signal spectrum 1811;and channel 1812 c comprises redundant spectrum 1810 c. Each channel1812 a-c carries the necessary amplitude, phase, and frequencyinformation to reconstruct modulating baseband signal 308 becauseredundant spectrums 1810 a-c carry such information. However, channel1812 b also carries jamming signal spectrum 1811 that may preventchannel 1812 b from being used to reconstruct modulating baseband signal308, depending on the relative signal strength of jamming signalspectrum 1811. Step 1706 was first discussed in relation to FIG. 17A,but is repeated here for convenience.

6.2.1.1.2 Structural Description:

FIG. 18I illustrates a block diagram of down-converter 1818, which isone embodiment of down-converter 1724 (FIG. 17I). Down-converter 1818includes mixer 1814 and local oscillator 1816. Preferably down-converter1818 translates redundant spectrums 1712 a-c to substantially lowerfrequencies by mixing redundant spectrums 1712 a-c with a localoscillating signal. In other words, down-converter 1818 is a structuralembodiment for performing the operational steps in flowchart 1800.However, it should be understood that the scope and spirit of the of thepresent invention includes other structural embodiments for performingthe steps of flowchart 1800. Flowchart 1800 will be revisited to furtherillustrate the present invention in view of the structural components indown-converter 1818.

In step 1702, (optional) medium interface module 1722 receives redundantspectrums 1712 a-c (FIG. 18B) from a communications medium. Step 1702and spectrums 1712 a-c were first discussed in FIGS. 17A-B respectively,and are repeated here for convenience.

In step 1802, a local oscillator 1816 generates local oscillating signal1806 (FIG. 18C). The local oscillating signal 1806 is preferably a sinewave (although other periodic waveforms could be used) with acharacteristic frequency f₃. The local oscillating signal 1806 has aspectrum 1808 (FIG. 18D) that is preferably a tone, but other spectrumscould be useful as is well known those skilled in the art(s). Also,preferably, f₃ is on the order of f₁.

In step 1804, mixer 1814 mixes redundant spectrums 1712 a-c with localoscillating signal 1806, resulting in redundant spectrums 1810 a-c (FIG.18E) that are located at frequencies (f₁−f₂)−f₃, f₁−f₃, and (f₁+f₂)−f₃respectively. Redundant spectrums 1810 a-c contain substantially similarinformation to that of spectrums 1810 a-c, except that they exist at asubstantially lower frequency; which is represented by the relativeplacement of break 1709 in frequency axis. Jamming signal spectrum 1711is also translated to a lower frequency since it is located within thebandwidth of spectrum 1712 b, resulting in jamming signal spectrum 1811.

Mixer 1814 typically includes at least one non-linear circuit elementincluding but not limited to a diode or a transistor. Mixer 1814 can beimplemented in multiple different types of circuit implementationsincluding but not limited to: single diode configurations, singlebalanced mixers, double balanced mixers, etc. These mixer circuitimplementations are well known to those skilled in the art(s) based onthe discussion given herein, and are within the scope and spirit of thepresent invention.

In step 1706, spectrum isolation module 1726 isolates redundantspectrums 1810 a-c from each other into channels 1812 a-c (shown inFIGS. 18F-18H). As such, channel 1812 a contains redundant spectrum 1810a; channel 1812 b contains redundant spectrum 1810 b and jamming signalspectrum 1811; and channel 1812 c contains redundant spectrum 1810 c.Each channel 1812 a-c carries the necessary amplitude, phase, andfrequency information to reconstruct modulating baseband signal 308because redundant spectrums 1714 a-c carry such information. However,channel 1712 b also carries jamming signal spectrum 1711 that mayprevent channel 1712 b from being used to reconstruct modulatingbaseband signal 308, depending on the relative signal strength ofjamming signal spectrum 1711.

6.2.1.2 Down-conversion Using a Universal Frequency Down-conversionModule

The following discussion describes down-converting redundant spectrumsusing a Universal Frequency Down-conversion Module. Redundant spectrumsrepresent an electromagnetic signal (EM signal), as will be understoodby those skilled in the art(s). The down-conversion by aliasing an EMsignal at an aliasing rate is further described in co-pending U.S.patent application entitled “Method and System for Down-converting anElectromagnetic Signal”, of common Assignee, Ser. No. 09/176,022, nowU.S. Pat. No. 6,061,551, issued May 9, 2000; which is incorporatedherein by reference in its entirety. A relevant portion of the abovementioned patent application is summarized below to describedown-converting an input signal (e.g. redundant spectrums 1712 a-c) toproduce a down-converted signal (e.g. redundant spectrums 1714 a-c) thatexists at a lower frequency.

FIG. 19A illustrates an aliasing module 1900 for down-conversion using auniversal frequency translation (UFT) module 1902 which down-converts anEM input signal 1904. In particular embodiments, aliasing module 1900includes a switch 1908 and a capacitor 1910. The electronic alignment ofthe circuit components is flexible. That is, in one implementation, theswitch 1908 is in series with input signal 1904 and capacitor 1910 isshunted to ground (although it may be other than ground inconfigurations such as differential mode). In a second implementation(see FIG. 19A-1), the capacitor 1910 is in series with the input signal1904 and the switch 1908 is shunted to ground (although it may be otherthan ground in configurations such as differential mode). Aliasingmodule 1900 with UFT module 1902 can be easily tailored to down-converta wide variety of electromagnetic signals using aliasing frequenciesthat are well below the frequencies of the EM input signal 1904.

In one implementation, aliasing module 1900 down-converts the inputsignal 1904 to an intermediate frequency (IF) signal. In anotherimplementation, the aliasing module 1900 down-converts the input signal1904 to a demodulated baseband signal. In yet another implementation,the input signal 1904 is a frequency modulated (FM) signal, and thealiasing module 1900 down-converts it to a non-FM signal, such as aphase modulated (PM) signal or an amplitude modulated (AM) signal. Eachof the above implementations is described below.

In an embodiment, the control signal 1906 includes a train of pulsesthat repeat at an aliasing rate that is equal to, or less than, twicethe frequency of the input signal 1904 In this embodiment, the controlsignal 1906 is referred to herein as an aliasing signal because it isbelow the Nyquist rate for the frequency of the input signal 1904.Preferably, the frequency of control signal 1906 is much less than theinput signal 1904.

The train of pulses 1918 of FIG. 19D control the switch 1908 to aliasthe input signal 1904 with the control signal 1906 to generate adown-converted output signal 1912. More specifically in an embodiment,switch 1908 closes on a first edge of each pulse 1920 of FIG. 19D andopens on a second edge of each pulse. When the switch 1908 is closed,the input signal 1904 is coupled to the capacitor 1910, and charge istransferred from the input signal to the capacitor 1910. The chargestored during successive pulses forms down-converted output signal 1912.

Exemplary waveforms are shown in FIGS. 19B-19F.

FIG. 19B illustrates an analog amplitude modulated (AM) carrier signal1914 that is an example of input signal 1904. For illustrative purposes,in FIG. 19C, an analog AM carrier signal portion 1916 illustrates aportion of the analog AM carrier signal 1914 on an expanded time scale.The analog AM carrier signal portion 1916 illustrates the analog AMcarrier signal 1914 from time t₀ to time t₁.

FIG. 19D illustrates an exemplary aliasing signal 1918 that is anexample of control signal 1906. Aliasing signal 1918 is on approximatelythe same time scale as the analog AM carrier signal portion 1916. In theexample shown in FIG. 19D, the aliasing signal 1918 includes a train ofpulses 1920 having negligible apertures that tend towards zero (theinvention is not limited to this embodiment, as discussed below). Thepulse aperture may also be referred to as the pulse width as will beunderstood by those skilled in the art(s). The pulses 1920 repeat at analiasing rate, or pulse repetition rate of aliasing signal 1918. Thealiasing rate is determined as described below, and further described inco-pending U.S. Patent Application entitled “Method and System forDown-converting an Electromagnetic Signal,” Application No. 09/176,022,now U.S. Pat. No. 6,061,551, issued May 9, 2000;

As noted above, the train of pulses 1920 (i.e., control signal 1906)control the switch 1908 to alias the analog AM carrier signal 1916(i.e., input signal 1904) at the aliasing rate of the aliasing signal1918. Specifically, in this embodiment, the switch 1908 closes on afirst edge of each pulse and opens on a second edge of each pulse. Whenthe switch 1908 is closed, input signal 1904 is coupled to the capacitor1910, and charge is transferred from the input signal 1904 to thecapacitor 1910. The charge transferred during a pulse is referred toherein as an under-sample. Exemplary under-samples 1922 formdown-converted signal portion 1924 (FIG. 19E) that corresponds to theanalog AM carrier signal portion 1916 (FIG. 19C) and the train of pulses1920 (FIG. 19D). The charge stored during successive under-samples of AMcarrier signal 1914 forms a down-converted signal 1924 (FIG. 19F) thatis an example of down-converted output signal 1912 (FIG. 19A). In FIG.19F, a demodulated baseband signal 1926 represents the demodulatedbaseband signal 1924 after filtering on a compressed time scale. Asillustrated, down-converted signal 1926 has substantially the same“amplitude envelope” as AM carrier signal 1914, but has lowercharacteristic frequency. Therefore, FIGS. 19B-19F illustratedown-conversion of AM carrier signal 1914.

The waveforms shown in FIGS. 19B-19F are discussed herein forillustrative purposes only, and are not limiting. Additional exemplarytime domain and frequency domain drawings, and exemplary methods andsystems of the invention relating thereto, are disclosed in co-pendingU.S. Patent Application entitled “Method and System for Down-convertingan Electromagnetic Signal,” Application No. 09/176,022, now U.S. Pat.No. 6,061,551, issued May 9, 2000;

The aliasing rate of control signal 1906 determines whether the inputsignal 1904 is down-converted to an IF signal, down-converted to ademodulated baseband signal, or down-converted from an FM signal to a PMor an AM signal. Generally, relationships between the input signal 1904,the aliasing rate of the control signal 1906, and the down-convertedoutput signal 1912 are illustrated below:

(Freq. of input signal 1904)=n•(Freq. of control signal 1906)+(Freq. ofdown-converted output signal 1912)

For the examples contained herein, only the “+” condition will bediscussed. The value of n represents a harmonic or sub-harmonic of inputsignal 1904 (e.g., n=0.5, 1, 2, 3, . . . ).

When the aliasing rate of control signal 1906 is off-set from thefrequency of input signal 1904, or off-set from a harmonic orsub-harmonic thereof, input signal 1904 is down-converted to an IFsignal. This is because the under-sampling pulses occur at differentphases of subsequent cycles of input signal 1904. As a result, theunder-samples form a lower frequency oscillating pattern. If the inputsignal 1904 includes lower frequency changes, such as amplitude,frequency, phase, etc., or any combination thereof, the charge storedduring associated under-samples reflects the lower frequency changes,resulting in similar changes on the down-converted IF signal. Forexample, to down-convert a 901 MHZ input signal to a 1 MHZ IF signal,the frequency of the control signal 1906 would be calculated as follows:

(Freq_(input)−Freq_(IF))/n=Freq_(control)(901 MHZ−1 MHZ)/n=900/n

For n=0.5, 1, 2, 3, 4, etc., the frequency of the control signal 1906would be substantially equal to 1.8 GHz, 900 MHZ, 450 MHZ, 300 MHZ, 225MHZ, etc.

Exemplary time domain and frequency domain drawings, illustratingdown-conversion of analog and digital AM, PM and FM signals to IFsignal, and exemplary methods and systems thereof₁ are disclosed inco-pending U.S. Patent Application entitled “Method and System forDown-converting an Electromagnetic Signal,” Application No. 09/176,022,now U.S. Pat. No. 6,061,551, issued May 9, 2000;

Alternatively, when the aliasing rate of the control signal 1906 issubstantially equal to the frequency of the input signal 1904, orsubstantially equal to a harmonic or sub-harmonic thereof, input signal1904 is directly down-converted to a demodulated baseband signal. Thisis because, without modulation, the under-sampling pulses occur at thesame point of subsequent cycles of the input signal 1904. As a result,the under-samples form a constant output baseband signal. If the inputsignal 1904 includes lower frequency changes, such as amplitude,frequency, phase, etc., or any combination thereof₁ the charge storedduring associated under-samples reflects the lower frequency changes,resulting in similar changes on the demodulated baseband signal. Forexample, to directly down-convert a 900 MHZ input signal to ademodulated baseband signal (i.e., zero IF), the frequency of thecontrol signal 1906 would be calculated as follows:

(Freq_(input)−Freq_(IF))/n=Freq_(control)(900 MHZ−0 MHZ)/n=900 MHZ/n

For n=0.5, 1, 2, 3, 4, etc., the frequency of the control signal 1906should be substantially equal to 1.8 GHz, 900 MHZ, 450 MHZ, 300 MHZ, 225MHZ, etc.

Exemplary time domain and frequency domain drawings, illustrating directdown-conversion of analog and digital AM and PM signals to demodulatedbaseband signals, and exemplary methods and systems thereof₁ aredisclosed in the co-pending U.S. Patent Application entitled “Method andSystem for Down-converting an Electromagnetic Signal,” Application No.09/176,022, now U.S. Pat. No. 6,061,551, issued May 9, 2000;

Alternatively, to down-convert an input FM signal to a non-FM signal, afrequency within the FM bandwidth must be down-converted to baseband(i.e., zero IF). As an example, to down-convert a frequency shift keying(FSK) signal (a sub-set of FM) to a phase shift keying (PSK) signal (asubset of PM), the mid-point between a lower frequency F₁ and an upperfrequency F₂ (that is, [(F₁+F₂)÷2]) of the FSK signal is down-convertedto zero IF. For example, to down-convert an FSK signal having F₁ equalto 899 MHZ and F₂ equal to 901 MHZ, to a PSK signal, the aliasing rateof the control signal 1906 would be calculated as follows:

Frequency of the input=(F₁+F₂)÷2=(899 MHZ+901 MHZ)÷2=900 MHZ

Frequency of the down-converted signal=0 (i.e., baseband)

(Freq_(input)−Freq_(IF))/n=Freq_(control)(900 MHZ−0 MHZ)/n=900 MHZ/n

For n=0.5, 1, 2, 3, etc., the frequency of the control signal 1906should be substantially equal to 1.8 GHz, 900 MHZ, 450 MHZ, 300 MHZ, 225MHZ, etc. The frequency of the down-converted PSK signal issubstantially equal to one half the difference between the lowerfrequency F₁ and the upper frequency F₂.

As another example, to down-convert a FSK signal to an amplitude shiftkeying (ASK) signal (a subset of AM), either the lower frequency F₁ orthe upper frequency F₂ of the FSK signal is down-converted to zero IF.For example, to down-convert an FSK signal having F₁ equal to 900 MHZand F₂ equal to 901 MHZ, to an ASK signal, the aliasing rate of thecontrol signal 1906 should be substantially equal to:

(900 MHZ−0 MHZ)/n=900 MHZ/n, or (901 MHZ−0 MHZ)/n=901 MHZ/n.

For the former case of 900 MHZ/n, and for n=0.5, 1, 2, 3, 4, etc., thefrequency of the control signal 1906 should be substantially equal to1.8 GHz, 900 MHZ, 450 MHZ, 300 MHZ, 225 MHZ, etc. For the latter case of901 MHZ/n, and for n=0.5, 1, 2, 3, 4, etc., the frequency of the controlsignal 1906 should be substantially equal to 1.802 GHz, 901 MHZ, 450.5MHZ, 300.333 MHZ, 225.25 MHZ, etc. The frequency of the down-convertedAM signal is substantially equal to the difference between the lowerfrequency F₁ and the upper frequency F₂ (i.e., 1 MHZ).

Exemplary time domain and frequency domain drawings, illustratingdown-conversion of FM signals to non-FM signals, and exemplary methodsand systems thereof, are disclosed in the co-pending U.S. PatentApplication entitled “Method and System for Down-converting anElectromagnetic Signal,” Application No. 09/176,022, now U.S. Pat. No.6,061,551, issued May 9, 2000;

In an embodiment, the pulses of the control signal 1906 have negligibleapertures that tend towards zero. This makes the UFT module 1902 a highinput impedance device. This configuration is useful for situationswhere minimal disturbance of the input signal may be desired.

In another embodiment, the pulses of the control signal 1906 havenon-negligible apertures that tend away from zero. This makes the UFTmodule 1902 a lower input impedance device. This allows the lower inputimpedance of the UFT module 1902 to be substantially matched with asource impedance of the input signal 1904. This also improves the energytransfer from the input signal 1904 to the converted output signal 1912,and hence the efficiency and signal to noise (s/n) ratio of UFT module1902.

Exemplary systems and methods for generating and optimizing the controlsignal 1906 and for otherwise improving energy transfer and s/n ratio,are disclosed in the co-pending U.S. Patent Application entitled “Methodand System for Down-converting an Electromagnetic Signal,” ApplicationNo. 09/176,022, now U.S. Pat. No. 6,061,551, issued May 9, 2000;

6.2.1.3 Other Embodiments

The down-conversion embodiments described above are provided forpurposes of illustration. These embodiments are not intended to limitthe invention. Alternate embodiments, differing slightly orsubstantially from those described herein, will be apparent to thoseskilled in the relevant art(s) based on the teachings given herein. Suchalternate embodiments include but are not limited to: superheterodynedown-conversion, digital down-conversion, and down-conversion usingspecialized mixers including harmonic mixers; and any well knowndown-conversion apparatus. Such alternate embodiments fall within thescope and spirit of the present invention.

6.2.2. Spectrum Isolation

Example embodiments for step 1706 of flowchart 1700 (FIG. 17A), andspectrum isolation module 1726 will be discussed in the followingsections. The example embodiments include isolating redundant spectrumsthat were isolated into separate channels by filtering each of theredundant spectrums.

6.2.2.1 Spectrum Isolation by Filtering Redundant Spectrums

The following discussion describes a method and system for isolatingredundant spectrums into separate channels by filtering each of theredundant spectrums.

6.2.2.1.1 Operational Description

FIG. 20A depicts flowchart 2000 for isolating redundant spectrums inseparate channels according to one embodiment of the present invention.In the following discussion, the steps in FIG. 20A will be discussed inrelation to the example signal diagrams in FIGS. 17D-17G. FIGS. 17D-Gwere initially described in relation to flowchart 1700, and are alsoapplicable to the discussion herein.

In step 1704, redundant spectrums 1712 a-c are translated to lowerintermediate frequencies; resulting in redundant spectrums 1714 a-c(FIG. 17D) that are located at frequencies F_(IFA), f_(IFB), andf_(IFC), respectively. These spectrums 1714 a-c are separated by f₂(Hz). Redundant spectrums 1714 a-c contain substantially the sameinformation as spectrums 1712 a-c, except that they exist at asubstantially lower frequencies, which is represented by the relativeplacement of break 1709 in frequency axis. Jamming signal spectrum 1711is also translated to a lower frequency since it is located within thebandwidth of spectrum 1712 b, resulting in jamming signal spectrum 1716.Step 1704 and spectrums 1714 a-c were first discussed in FIG. 17A andFIG. 17D, respectively, and are repeated here for convenience.

In step 2002, redundant spectrum 1714 a-c are filtered into separatechannels, resulting in channels 1718 a-c (shown in FIGS. 17E-17G). Assuch, channel 1718 a comprises redundant spectrum 1714 a; channel 1718 bcomprises redundant spectrum 1714 b and jamming signal spectrum 1716;and channel 1718 c comprises redundant spectrum 1714 c. Each channel1718 a-c carries the necessary amplitude, phase, and frequencyinformation to reconstruct modulating baseband signal 308 becauseredundant spectrums 1714 a-c carry such information. However, channel1718 b also carries jamming signal spectrum 1716 that may preventchannel 1718 b from being used to reconstruct modulating baseband signal308, depending on the relative signal strength of jamming signalspectrum 1716.

In step 1708, demodulated baseband signal 1720 is extracted fromchannels 1718 a-c, where demodulated baseband signal 1720 issubstantially similar to modulated baseband signal 308.

6.2.2.1.2 Structural Description:

FIG. 20B illustrates down-converter 1724, filter bank 2004, and signalextraction module 1728 associated with receiver module 1730 (FIG. 17I),where filter bank 2004 is one embodiment of spectrum isolation module1726. Filter bank 2004 includes band pass filters 2006 a-c. Preferablyfilter bank 2004 separates redundant spectrums 1714 a-c into channels1718 a-c. In other words, filter bank 2004 is a structural embodimentfor performing the operational step 2002 in flowchart 2000 (and step1706 in flowchart 1700). However, it should be understood that the scopeand spirit of the of the present invention includes other structuralembodiments for performing the step 2002 of flowchart 2000. Flowchart2000 will be revisited to further illustrate the present invention inview of the structural components in receiver module 1730.

In step 1704, down-converter 1724 translates redundant spectrums 1712a-c to a lower intermediate frequencies. This results in redundantspectrums 1714 a-c (FIG. 17D) that are located at frequencies f_(IFA),f_(IFB), and f_(IFC), respectively, that are separated by f₂ (Hz).Redundant spectrums 1714 a-c are substantially similar to spectrums 1712a-c, except that they exist at a substantially lower frequency; which isrepresented by the relative placement of break 1709 in frequency axis.Jamming signal spectrum 1711 is also translated to a lower frequencysince it is located within the bandwidth of spectrum 1712 b, resultingin jamming signal spectrum 1716. Step 1704 and spectrums 1714 a-c werefirst discussed in FIG. 17A and FIG. 17B, respectively, and are repeatedhere for convenience.

In step 2002, filter bank 2004 filters redundant spectrum 1714 a-c intoseparate channels 1718 a-c that contain spectrums 1714 a-c,respectively. In doing so, band pass filter 2006 a has center frequencyat f_(IFA), and a passband that is sufficient to pass spectrum 1714 a,but rejects the remaining redundant spectrums 1714 b,c. Band pass filter2006 b has a center frequency at f_(IFB), and a passband that issufficient to pass spectrum 1714 b, but rejects the remaining redundantspectrums 1714 a,c. As such, band pass filter 2006 b will also passjamming signal spectrum 1716 because it is withing the frequencybandwidth of redundant spectrum 1714 b. Band pass filter 2006 c has acenter frequency at f_(IFC), and a passband that is sufficient to passspectrum 1714 c, but rejects the remaining redundant spectrums 1714 a,b.

The result of step 2002 is that channel 1718 a comprises redundantspectrum 1714 a; channel 1718 b comprises redundant spectrum 1714 b andjamming signal spectrum 1716; and channel 1718 c comprises redundantspectrum 1714 c. Each channel 1718 a-c carries the necessary amplitude,phase, and frequency information to reconstruct modulating basebandsignal 308 because redundant spectrums 1714 a-c carry such information.However, channel 1718 b also carries jamming signal spectrum 1716 thatmay prevent channel 1718 b from being used to reconstruct modulatingbaseband signal 308, depending on the relative signal strength of thejamming signal spectrum 1716.

In one embodiment described in section 6.2.1.1, down-converter 1724includes a mixer 1814 and a local oscillator 1816 with a characteristicfrequency f₃. When mixer 1814 is used, f_(IFA), f_(IFB), and f_(IFC) aresubstantially equal to (f₁−f₂)−f₃, (f₁−f₃), and (f₁+f₂)−f₃ as describedin section 6.2.1.1. As such, filters 2006 a-c should be centeredaccordingly, as would be well known to those skilled in the art(s) basedon the discussion herein. In practice, it is possible to design andimplement the filter bank 2004 using many well known filter techniquessince f₁, f₂, and f₃ are known.

Furthermore, filter bank 2004 depicts three bandpass 2006 a-c to processthree redundant spectrums 1714 a-c. This is for example only. As statedin section 6.2.1.1, any number of redundant spectrums can be transmitted(and thus received) over a communications medium. As such, filter bank2004 can be scaled to include any number of band pass filters to processany number of redundant spectrums received by (optional) mediuminterface module 1722, as would be well known to those skilled in theart(s) based on the discussion given herein. The invention is notlimited to the use of bandpass filters. In other embodiments, other wellknown filter techniques can be used.

In step 1708, demodulated baseband signal 1720 is extracted fromchannels 1718 a-c, where demodulated baseband signal 1720 issubstantially similar to modulated baseband signal 308.

6.2.2.2. Down-conversion and Spectrum Isolation using a UnifiedDown-converting and Filtering Module (UDF)

In one embodiment, one or more unified down-converting and filteringmodules (UDF) replace the down-converter 1724, and the spectrumisolation module 1726. A single UDF module both down-converts andfilters a redundant spectrum in an integrated manner. FIG. 20Cillustrates the relative placement of UDF modules 2008 a-c in receiver1730 (FIG. 17I, see also FIG. 20B) between (optional) medium interfacemodule 1722 and signal extraction module 1720, where a UDF module isimplemented for each received redundant spectrum (or each spectrum ofinterest) according to one embodiment of the present invention.Down-converting and filtering in a unified manner using a UDF module isfurther described in co-pending U.S. patent application entitled“Integrated Frequency Translation and Selectivity”, of common assignee,Ser. No. 09/175,966, now U.S. Pat. No. 6,049,706, issued April 11, 2000;and which is herein incorporated by reference in its entirety. Arelevant portion of the above mentioned application is summarized belowto describe down-converting and filtering an input signal (e.g.redundant spectrums 1712 a-c) to an output signal (e.g. redundantspectrums 1714 a-c). The summary of the UDF module is as follows.

The present invention includes a unified down-converting and filtering(UDF) module that performs frequency selectivity and frequencytranslation in a unified (i.e., integrated) manner. By operating in thismanner, the invention achieves high frequency selectivity prior tofrequency translation (the invention is not limited to this embodiment).The invention achieves high frequency selectivity at substantially anyfrequency, including but not limited to RF (radio frequency) and greaterfrequencies. It should be understood that the invention is not limitedto this example of RF and greater frequencies. The invention isintended, adapted, and capable of working with lower than radiofrequencies.

FIG. 24 is a conceptual block diagram of a UDF module 2402 according toan embodiment of the present invention. The UDF module 2402 performs atleast frequency translation and frequency selectivity.

The effect achieved by the UDF module 2402 is to perform the frequencyselectivity operation prior to the performance of the frequencytranslation operation. Thus, the UDF module 2402 effectively performsinput filtering.

According to embodiments of the present invention, such input filteringinvolves a relatively narrow bandwidth. For example, such inputfiltering may represent channel select filtering, where the filterbandwidth may be, for example, 50 KHz to 150 KHz. It should beunderstood, however, that the invention is not limited to thesefrequencies. The invention is intended, adapted, and capable ofachieving filter bandwidths of less than and greater than these values.

In embodiments of the invention, input signals 2404 received by the UDFmodule 2402 are at radio frequencies. The UDF module 2402 effectivelyoperates to input filter these RF input signals 2404. Specifically, inthese embodiments, the UDF module 2402 effectively performs input,channel select filtering of the RF input signal 2404. Accordingly, theinvention achieves high selectivity at high frequencies.

The UDF module 2402 effectively performs various types of filtering,including but not limited to bandpass filtering, low pass filtering,high pass filtering, notch filtering, all pass filtering, band stopfiltering, etc., and combinations thereof.

Conceptually, the UDF module 2402 includes a frequency translator 2408.The frequency translator 2408 conceptually represents that portion ofthe UDF module 2402 that performs frequency translation (downconversion).

The UDF module 2402 also conceptually includes an apparent input filter2406 (also sometimes called an input filtering emulator). Conceptually,the apparent input filter 2406 represents that portion of the UDF module2402 that performs input filtering.

In practice, the input filtering operation performed by the UDF module2402 is integrated with the frequency translation operation. The inputfiltering operation can be viewed as being performed concurrently withthe frequency translation operation. This is a reason why the inputfilter 2406 is herein referred to as an “apparent” input filter 2406.

The UDF module 2402 of the present invention includes a number ofadvantages. For example, high selectivity at high frequencies isrealizable using the UDF module 2402. This feature of the invention isevident by the high Q factors that are attainable. For example, andwithout limitation, the UDF module 2402 can be designed with a filtercenter frequency f_(C) on the order of 900 MHZ, and a filter bandwidthon the order of 50 KHz. This represents a Q of 18,000 (Q is equal to thecenter frequency divided by the bandwidth).

It should be understood that the invention is not limited to filterswith high Q factors. The filters contemplated by the present inventionmay have lesser or greater Qs, depending on the application, design,and/or implementation. Also, the scope of the invention includes filterswhere Q factor as discussed herein is not applicable.

The invention exhibits additional advantages. For example, the filteringcenter frequency f_(C) of the UDF module 2402 can be electricallyadjusted, either statically or dynamically.

Also, the UDF module 2402 can be designed to amplify input signals.

Further, the UDF module 2402 can be implemented without large resistors,capacitors, or inductors. Also, the UDF module 2402 does not requirethat high tolerances be maintained on its individual components, i.e.,its resistors, capacitors, inductors, etc. As a result, the architectureof the UDF module 2402 is friendly to integrated circuit designtechniques and processes.

The features and advantages exhibited by the UDF module 2402 areachieved at least in part by adopting a new technological paradigm withrespect to frequency selectivity and translation. Specifically,according to the present invention, the UDF module 2402 performs thefrequency selectivity operation and the frequency translation operationas a single, unified (integrated) operation. According to the invention,operations relating to frequency translation also contribute to theperformance of frequency selectivity, and vice versa.

According to embodiments of the present invention, the UDF modulegenerates an output signal from an input signal using samples/instancesof the input signal and samples/instances of the output signal.

More particularly, first, the input signal is sampled. This input sampleincludes information (such as amplitude, phase, etc.) representative ofthe input signal existing at the time the sample was taken.

As described further below, the effect of repetitively performing thisstep is to translate the frequency (that is, down-convert) of the inputsignal to a desired lower frequency, such as an intermediate frequency(IF) or baseband.

Next, the input sample is held (that is, delayed).

Then, one or more delayed input samples (some of which may have beenscaled) are combined with one or more delayed instances of the outputsignal (some of which may have been scaled) to generate a currentinstance of the output signal.

Thus, according to a preferred embodiment of the invention, the outputsignal is generated from prior samples/instances of the input signaland/or the output signal. (It is noted that, in some embodiments of theinvention, current samples/instances of the input signal and/or theoutput signal may be used to generate current instances of the outputsignal.). By operating in this manner, the UDF module preferablyperforms input filtering and frequency down-conversion in a unifiedmanner.

FIG. 26 illustrates an example implementation of the unifieddown-converting and filtering (UDF) module 2622. The UDF module 2622performs the frequency translation operation and the frequencyselectivity operation in an integrated, unified manner as describedabove, and as further described below.

In the example of FIG. 26, the frequency selectivity operation performedby the UDF module 2622 comprises a band-pass filtering operationaccording to EQ. 1, below, which is an example representation of aband-pass filtering transfer function.

 VO=α ₁ z ⁻¹ VI−β ₁ z ⁻¹ VO−β ₀ z ⁻² VO  EQ. 1

It should be noted, however, that the invention is not limited toband-pass filtering. Instead, the invention effectively performs varioustypes of filtering, including but not limited to bandpass filtering, lowpass filtering, high pass filtering, notch filtering, all passfiltering, band stop filtering, etc., and combinations thereof. As willbe appreciated, there are many representations of any given filter type.The invention is applicable to these filter representations. Thus, EQ. 1is referred to herein for illustrative purposes only, and is notlimiting.

The UDF module 2622 includes a down-convert and delay module 2624, firstand second delay modules 2628 and 2630, first and second scaling modules2632 and 2634, an output sample and hold module 2636, and an (optional)output smoothing module 2638. Other embodiments of the UDF module willhave these components in different configurations, and/or a subset ofthese components, and/or additional components. For example, and withoutlimitation, in the configuration shown in FIG. 26, the output smoothingmodule 2638 is optional.

As further described below, in the example of FIG. 26, the down-convertand delay module 2624 and the first and second delay modules 2628 and2630 include switches that are controlled by a clock having two phases,φ₁ and φ₂. φ₁ and φ₂ preferably have the same frequency, and arenon-overlapping (alternatively, a plurality such as two clock signalshaving these characteristics could be used). As used herein, the term“non-overlapping” is defined as two or more signals where only one ofthe signals is active at any given time. In some embodiments, signalsare “active” when they are high. In other embodiments, signals areactive when they are low.

Preferably, each of these switches closes on a rising edge of φ₁ or φ₂,and opens on the next corresponding falling edge of φ₁ or φ₂. However,the invention is not limited to this example. As will be apparent topersons skilled in the relevant art(s), other clock conventions can beused to control the switches.

In the example of FIG. 26, it is assumed that α₁ is equal to one. Thus,the output of the down-convert and delay module 2624 is not scaled. Asevident from the embodiments described above, however, the invention isnot limited to this example.

The example UDF module 2622 has a filter center frequency of 900.2 MHZand a filter bandwidth of 570 KHz. The pass band of the UDF module 2622is on the order of 899.915 MHZ to 900.485 MHZ. The Q factor of the UDFmodule 2622 is approximately 1579 (i.e., 900.2 MHZ divided by 570 KHz).

The operation of the UDF module 2622 shall now be described withreference to a Table 2502 (FIG. 25) that indicates example values atnodes in the UDF module 2622 at a number of consecutive time increments.It is assumed in Table 2502 that the UDF module 2622 begins operating attime t−1. As indicated below, the UDF module 2622 reaches steady state afew time units after operation begins. The number of time unitsnecessary for a given UDF module to reach steady state depends on theconfiguration of the UDF module, and will be apparent to persons skilledin the relevant art(s) based on the teachings contained herein.

At the rising edge of φ₁ at time t−1, a switch 2650 in the down-convertand delay module 2624 closes. This allows a capacitor 2652 to charge tothe current value of an input signal, VI_(t−1) such that node 2602 is atVI_(t−1). This is indicated by cell 2504 in FIG. 25. In effect, thecombination of the switch 2650 and the capacitor 2652 in thedown-convert and delay module 2624 operates to translate the frequencyof the input signal VI to a desired lower frequency, such as IF orbaseband. Thus, the value stored in the capacitor 2652 represents aninstance of a down-converted image of the input signal VI.

The manner in which the down-convert and delay module 2624 performsfrequency down-conversion is further described elsewhere in thisapplication, and is additionally described in pending U.S. application“Methods and Systems for Down-Converting Electromagnetic Signals,” Ser.No. 09/176,022, now U.S. Pat. No. 6,061,551, issued May 9, 2000; whichis herein incorporated by reference in its entirety.

Also at the rising edge of φ₁ at time t−1, a switch 2658 in the firstdelay module 2628 closes, allowing a capacitor 2660 to charge toVO_(t−1), such that node 2606 is at VO_(t−1). This is indicated by cell2506 in Table 2502. (In practice, VO_(t−1) is undefined at this point.However, for ease of understanding, VO_(t−1) shall continue to be usedfor purposes of explanation.)

Also at the rising edge of φ₁ at time t−1, a switch 2666 in the seconddelay module 2630 closes, allowing a capacitor 2668 to charge to a valuestored in a capacitor 2664. At this time, however, the value incapacitor 2664 is undefined, so the value in capacitor 2668 isundefined. This is indicated by cell 2507 in table 2502.

At the rising edge of φ₂ at time t−1, a switch 2654 in the down-convertand delay module 2624 closes, allowing a capacitor 2656 to charge to thelevel of the capacitor 2652. Accordingly, the capacitor 2656 charges toVI_(t−1), such that node 2604 is at VI_(t−1). This is indicated by cell2510 in Table 2502.

The UDF module 2622 may optionally include a unity gain module 2690Abetween capacitors 2652 and 2656. The unity gain module 2690A operatesas a current source to enable capacitor 2656 to charge without drainingthe charge from capacitor 2652. For a similar reason, the UDF module2622 may include other unity gain modules 2690B-2690G. 1t should beunderstood that, for many embodiments and applications of the invention,these unity gain modules 2690A-2690G are optional. The structure andoperation of the unity gain modules 2690 will be apparent to personsskilled in the relevant art(s).

Also at the rising edge of φ₂ at time t−1, a switch 2662 in the firstdelay module 2628 closes, allowing a capacitor 2664 to charge to thelevel of the capacitor 2660. Accordingly, the capacitor 2664 charges toVO_(t−1), such that node 2608 is at VO_(t−1). This is indicated by cell2514 in Table 2502.

Also at the rising edge of φ₂ at time t−1, a switch 2670 in the seconddelay module 2630 closes, allowing a capacitor 2672 to charge to a valuestored in a capacitor 2668. At this time, however, the value incapacitor 2668 is undefined, so the value in capacitor 2672 isundefined. This is indicated by cell 2515 in table 2502.

At time t, at the rising edge of φ₁, the switch 2650 in the down-convertand delay module 2624 closes. This allows the capacitor 2652 to chargeto VI_(t), such that node 2602 is at VI_(t). This is indicated in cell2516 of Table 2502.

Also at the rising edge of φ₁ at time t, the switch 2658 in the firstdelay module 2628 closes, thereby allowing the capacitor 2660 to chargeto VO_(t). Accordingly, node 2606 is at VO_(t). This is indicated incell 2520 in Table 2502.

Further at the rising edge of φ₁ at time t, the switch 2666 in thesecond delay module 2630 closes, allowing a capacitor 2668 to charge tothe level of the capacitor 2664. Therefore, the capacitor 2668 chargesto VO_(t−1), such that node 2610 is at VO_(t−1). This is indicated bycell 2524 in Table 2502.

At the rising edge of φ₂ at time t, the switch 2654 in the down-convertand delay module 2624 closes, allowing the capacitor 2656 to charge tothe level of the capacitor 2652. Accordingly, the capacitor 2656 chargesto VI_(t), such that node 2604 is at VI_(t). This is indicated by cell2528 in Table 2502.

Also at the rising edge of φ₂ at time t, the switch 2662 in the firstdelay module 2628 closes, allowing the capacitor 2664 to charge to thelevel in the capacitor 2660. Therefore, the capacitor 2664 charges toVO_(t), such that node 2608 is at VO_(t). This is indicated by cell 2532in Table 2502.

Further at the rising edge of φ₂ at time t, the switch 2670 in thesecond delay module 2630 closes, allowing the capacitor 2672 in thesecond delay module 2630 to charge to the level of the capacitor 2668 inthe second delay module 2630. Therefore, the capacitor 2672 charges toVO_(t−1), such that node 2612 is at VO_(t−1). This is indicated in cell2536 of FIG. 25.

At time t+1, at the rising edge of φ₁ the switch 2650 in thedown-convert and delay module 2624 closes, allowing the capacitor 2652to charge to VI_(t+1). Therefore, node 2602 is at VI_(t+1), as indicatedby cell 2538 of Table 2502.

Also at the rising edge of φ₁ at time t+1, the switch 2658 in the firstdelay module 2628 closes, allowing the capacitor 2660 to charge toVO_(t+1). Accordingly, node 2606 is at VO_(t+1), as indicated by cell2542 in Table 2502.

Further at the rising edge of φ₁ at time t+1, the switch 2666 in thesecond delay module 2630 closes, allowing the capacitor 2668 to chargeto the level of the capacitor 2664. Accordingly, the capacitor 2668charges to VO_(t), as indicated by cell 2546 of Table 2502.

In the example of FIG. 26, the first scaling module 2632 scales thevalue at node 2608 (i.e., the output of the first delay module 2628) bya scaling factor of −0.1. Accordingly, the value present at node 2614 attime t+1 is −0.1*VO_(t). Similarly, the second scaling module 2634scales the value present at node 2612 (i.e., the output of the secondscaling module 2630) by a scaling factor of −0.8. Accordingly, the valuepresent at node 2616 is −0.8*VO_(t−1) at time t+1.

At time t+1, the values at the inputs of the summer 2626 are: VI_(t) atnode 2604, −0.1*VO_(t) at node 2614, and −0.8*VO_(t−1) at node 2616 (inthe example of FIG. 26, the values at nodes 2614 and 2616 are summed bya second summer 2625, and this sum is presented to the summer 2626).Accordingly, at time t+1, the summer generates a signal equal toVI_(t)−0.1*VO_(t)−0.8*VO_(t−1).

At the rising edge of φ₁ at time t+1, a switch 2690 in the output sampleand hold module 2636 closes, thereby allowing a capacitor 2692 to chargeto VO_(t+1). Accordingly, the capacitor 2692 charges to VO_(t+1), whichis equal to the sum generated by the adder 2626. As just noted, thisvalue is equal to: VI_(t)−0.1*VO_(t)−0.8*VO_(t−1). This is indicated incell 2550 of Table 2502. This value is presented to the output smoothingmodule 2638, which smooths the signal to thereby generate the instanceof the output signal VO_(t+1). It is apparent from inspection that thisvalue of VO_(t+1) is consistent with the band pass filter transferfunction of EQ. 1.

6.2.2.3 Other Embodiments

The spectrum isolation embodiments described above are provided forpurposes of illustration. These embodiments are not intended to limitthe invention. Alternate embodiments, differing slightly orsubstantially from those described herein, will be apparent to thoseskilled in the relevant art(s) based on the teachings given herein. Suchalternate embodiments fall within the scope and spirit of the presentinvention.

6.2.3 Signal extraction

Example embodiments for step 1708 of flowchart 1700 (FIG. 17A), andsignal extraction module 1728 will be discussed in the following sectionand subsections. The example embodiments include extracting ademodulated baseband signal from redundant spectrums that are isolatedinto separate channels.

6.2.3.1 Signal Extraction by Demodulation, With Error Checking and/orError Correction

The following description includes a system and method for extractingthe demodulated baseband signal from redundant spectrums that wereisolated into separate channels. The system and method includesdemodulating redundant spectrums along with error checking, and/or errorcorrection.

6.2.3.1.1 Operational Description

FIG. 21 A depicts flowchart 2100 for extracting the demodulated basebandsignal 1720 (FIG. 21H) from channels 1718 a-c (FIGS. 21E-G). Demodulatedbaseband signal 1720 was first presented in FIG. 17H, and isre-illustrated in FIG. 21H for convenience. Similarly, channels 1718 a-cwere first presented in FIGS. 17E-G, respectively, and arere-illustrated in FIGS. 21B-D for convenience. In the followingdiscussion, the steps in FIG. 21A will be discussed in relation to theexample signal diagrams in FIGS. 21B-21H.

In step 1706, redundant spectrum 1714 a-c are isolated from each otherinto separate channels, resulting in channels 1718 a-c (shown in FIGS.21B-21D). As such, channel 1718 a comprises redundant spectrum 1714 a;channel 1718 b comprises redundant spectrum 1714 b and jamming signalspectrum 1716; and channel 1718 c comprises redundant spectrum 1714 c.Each channel 1718 a-c carries the necessary amplitude, phase, andfrequency information to reconstruct modulating baseband signal 308because redundant spectrums 1714 a-c carry such information. However,channel 1718 b also carries jamming signal spectrum 1716 that mayprevent channel 1718 b from being used to reconstruct modulatingbaseband signal 308, depending on the relative signal strength ofjamming signal spectrum 1716. Step 1706 and channels 1718 a-c were firstdiscussed in FIGS. 17A and FIGS. 17E-G, respectively and arere-illustrated here for convenience.

In step 2102, redundant spectrums 1714 a-c (in channels 1718 a-c,respectively) are preferably independently demodulated (or decoded),resulting in demodulated baseband signals 2108 a-c (FIGS. 21E-G),respectively. The type of demodulation implemented in step 2108 isconsistent with the type of modulation scheme used to generate redundantspectrums 1714 a-c. Demodulation techniques for standard modulationschemes include but are not limited to AM, ASK, FM, FSK, PM, PSK, etc.,combinations thereof₁ and other modulation schemes will be apparent tothose skilled in the art(s) based on the teachings given herein.

FIGS. 21E and 21G depict demodulated baseband signals 2108 a and 2108 cthat are substantially similar to modulated baseband signal 308 (FIG.3A), as is desired. However, FIG. 21F depicts a demodulated basebandsignal 2108 b that is not substantially similar to modulating basebandsignal 308, as would be expected from the presence of jamming signalspectrum 1716 in channel 1718 b, from which the demodulated basebandsignal 2108 b is derived.

In step 2104, each demodulated baseband signal 2108 a-c is analyzed todetect errors. In one embodiment, when a demodulated baseband signal isdetermined to be erroneous, an associated error flag is set. The errorflag for each demodulated baseband signal can then be examined in step2106 to select an error-free demodulated baseband signal.

Any of the many available error detection schemes can be used to detecterrors in step 2104. Furthermore, in some instances, methodologies canbe used to correct detected errors in digital signals. Some effectiveerror detection schemes for digital and analog demodulated basebandsignals will be discussed below.

Cylic Redundancy Check (CRC) and parity check can be used to detecterrors in demodulated baseband signals that are digital signals. A shortsummary of each follows. CRC examines a bit stream (prior totransmission over a communications medium) and calculates an n-bit CRCcharacter according to a specific mathematical relationship based on theexamined bit stream. The CRC character is then transmitted with theexamined bit stream over the communications medium. The same calculationis performed at the receiver. If the CRC character determined by thereceiver agrees with that sent with the bit stream, then the bit streamis determined to be error free. If there is disagreement, then an errorhas been introduced. Parity check also generates n-bit characterassociated with a bit stream; where the parity check character is basedon the number of logic “1”s or “0”s in the bit stream. The scope andspirit of the present invention includes all other errorchecking/correction schemes including but not limited to check sum aswill be understood by those skilled in the art(s) based on thediscussion given herein.

Error detection for analog demodulated baseband signals can beimplemented through various encoder/decoder and pattern recognitionschemes. In one embodiment, this is done by examining the separateddemodulated baseband signals to determine a consensus signal shape. Eachdemodulated baseband signal can then be compared with the consensussignal, where any demodulated baseband signal that is substantiallydifferent from the consensus signal is deemed erroneous. Implementationof this scheme on demodulated baseband signals 2108 a-c (FIGS. 21E-21G)will result in baseband signal 2108 b being deemed as erroneous.

In another embodiment, error detection for analog signals isaccomplished by monitoring a pilot tone that is embedded in theredundant spectrums from which the demodulated baseband signals aregenerated. After calibration, any degradation in pilot tone may beevidence of signal interference.

In another embodiment, error detection for analog signals isaccomplished by passing each demodulated baseband signal through a highpass filter to select the (out-of-band) high frequency components ineach demodulated baseband signal. Ideally, the amplitude of theseout-of-band frequency components is small. Therefore, if the power levelof these out-of-band frequency components is above some threshold level,then the demodulated baseband signal may be corrupted with unwantedinterference. This method of error detection would flag demodulatedbaseband signal 2108 b (FIG. 21F) as erroneous.

In step 2106, a substantially error-free demodulated baseband signal isselected; resulting in demodulated baseband signal 1720 (FIG. 17H). Inone embodiment, a particular demodulated baseband signal issubstantially error-free if it is sufficiently similar to (i.e.representative of) the modulating baseband signal (associated with thetransmitted redundant spectrums in step 306) for the needs of theapplication. Therefore, in one embodiment, the level of similarity isapplication specific. For example and without limitation, voicecommunication may require less similarity than data communications aswill be understood by those skilled in the relevant art(s). In theexample illustrated in FIGS. 21E-G, either demodulated baseband signal2108 a or 2108 c can be selected as demodulated baseband signal 1720.

In one embodiment, step 2106 selects a substantially error-freedemodulated baseband signal through a process of elimination. This canbe done by examining status of the error flag generated in step 2104 foreach demodulated baseband signal. If the error flag is set, then theassociated demodulated baseband signal is eliminated from consideration.This embodiment is further illustrated by flowchart 2200 (FIG. 22) thatis discussed below.

Flowchart 2200 (FIG. 22A) is an operational process for selecting anerror-free demodulated baseband signal through a process of elimination,and is one embodiment of step 2106 in flowchart 2100 (FIG. 21A).Flowchart 2200 will be discussed as follows.

In step 2202, a plurality of demodulated baseband signals and associatederror flags are accepted. The demodulated baseband signals arepreferable isolated in channels A-N. For example, demodulated basebandsignals 2108 a-c can be described as existing in channels thatcorrespond to the their corresponding letter “a-c”. The error flagassociated with each demodulated baseband signal is preferably generatedas described in step 2104 above.

In step 2204, it is determined whether the error flag associated withthe demodulated baseband signal in channel A is set. If yes, then instep 2206, the demodulated baseband signal in channel A is eliminatedfrom consideration, after which control flows to step 2208. If no, thenflowchart 2200 sends control directly to step 2208.

In step 2208, it is determined whether the error flag associated withthe demodulated baseband signal in channel B is set. If yes, then instep 2210, the demodulated baseband signal in channel B is eliminatedfrom consideration, after which control flows to step 2212. If no, thenflowchart 2200 sends control directly to step 2212.

In step 2212, it is determined whether the error flag associated withthe demodulated baseband signal in channel C is set. If yes, then instep 2214, the demodulated baseband signal in channel C is eliminatedfrom consideration, after which control flows to step 2215. If no, thenflowchart 2200 sends control directly to step 2215.

The process described above continues until the N^(th) channel isreached. In step 2215, it is determined whether the error flagassociated with demodulated baseband signal in channel N is set. If yes,then in step 2216, the demodulated baseband signal in channel N iseliminated from consideration, after which control flows to step 2217.If no, then flowchart 2200 sends control directly to step 2217.

In step 2217, it is determined whether at least one demodulated basebandsignal is viable (i.e., at least one that has not been eliminated). Ifyes, then control flows to step 2218. If no, then control flows to step2219, where the process follows application specific instructions toaddress the situation where all de-modulated baseband signals have beendetermined to be erroneous. After which, the process ends in step 2220.

In step 2218, a demodulated baseband signal is selected from thedemodulated baseband signals that are still under consideration. If morethan one demodulated baseband signal is still viable, then the selectioncan be done according to the channel order (i.e. select channel A overchannel C), or inverse channel order (i.e. select channel C over channelA), or any other means of selection including selection based on highestpower level.

The selection process described by flowchart 2200 will now be applied todemodulated baseband signal 2108 a-c in FIGS. 21 E-G, respectively. Indoing so, the error flag associated with demodulated baseband signal2108 b in channel B will be set. Therefore, step 2208 will eliminatedemodulated baseband signal 2108 b from consideration. This leaves thechoice between demodulated baseband signals 2108 a and 2108 c. In oneembodiment, demodulated baseband signal 2108 a is selected because it isin Channel A, and Channel A was the first channel examined. In anotherembodiment, demodulated baseband signal 2108 c is selected because it isin Channel C, and was the last channel examined. In another embodiment,channel power level is monitored, and the channel with the strongestdemodulated baseband signal is selected. Either way a substantiallyerror-free demodulated baseband signal is selected that is substantiallysimilar to the modulating baseband signal used to generate the redundantspectrums.

Flowchart 2222 (FIG. 22B) is an alternative operational process forselecting a substantially error-free demodulated baseband signal througha process of elimination, and is one embodiment of step 2106 inflowchart 2100 (FIG. 21A). Flowchart 2222 will be discussed as follows.

In step 2224, a plurality of demodulated baseband signals and associatederror flags are accepted. The demodulated baseband signals arepreferable isolated in channels A-N. For example, demodulated basebandsignals 2108 a-c can be described as existing in channels thatcorrespond to the their corresponding letter “a-c”. The error flagassociated with each demodulated baseband signal is preferably generatedas described in step 2104 above.

In step 2226, it is determined whether the error flag associated withthe demodulated baseband signal in channel A is set. If yes, thencontrol flows to step 2232. If no, then in step 2228, the demodulatedbaseband signal in channel A is selected as a substantially error-freedemodulated baseband signal, after which flowchart processing ends instep 2230. As stated earlier, a particular demodulated baseband signalis substantially error-free if it is sufficiently similar to and/orrepresentative of the modulating baseband signal as needed for thespecific application in use.

In step 2232, it is determined whether the error flag associated withthe demodulated baseband signal in channel B is set. If yes, thencontrol flows to step 2238, and the demodulated baseband signal inchannel B is eliminated from consideration. If no, then in step 2234,the demodulated baseband signal in channel 25B is selected as asubstantially error-free demodulated baseband signal, after whichprocessing ends in step 2236.

In step 2238, it is determined whether the error flag associated withthe demodulated baseband signal in channel C is set. If yes, thencontrol flows to step 2244, and the demodulated baseband signal inchannel C is eliminated from consideration. If no, then in step 2240,the demodulated baseband signal in channel C is selected as asubstantially error-free demodulated baseband signal, after whichprocessing ends in step 2242.

The process described above continues until the N^(th) channel isreached. In step 2244, it is determined whether the error flagassociated with the demodulated baseband signal in channel N is set. Ifyes, then control flows to step 2250, and the demodulated basebandsignal in channel N is eliminated from consideration. If no, then instep 2246, the demodulated baseband signal in channel N is selected as asubstantially error-free demodulated baseband signal, after whichprocessing ends in step 2248.

If the process reaches step 2250, then all the error flags for theavailable channels have been checked and determined to be set, meaningthat all the available de-modulated baseband signals have beendetermined to contain errors. In such case, step 2250 followsapplication specific instructions, after which processing ends in step2252. In one embodiment, the application specific instruction may be arequest for re-transmission.

6.2.3.1.2 Structural Description:

FIG. 21I illustrates spectrum isolation module 1726, and signalextraction module 1728 from receiver module 1730 (FIG. 17I), where inone embodiment signal extraction module 1728 includes signal extractionmodule 2110. Signal extraction module 2110 includes demodulators 2112a-c, error check modules 2114 a-c, and arbitration module 2116.Preferably signal extraction module 2110 receives redundant spectrums1714 a-c and extracts demodulated baseband signal 1720. In other words,signal extraction module 1728 is a structural embodiment for performingthe operational steps 2102-2106 in flowchart 2100. However, it should beunderstood that the scope and spirit of the of the present inventionincludes other structural embodiments for performing the steps 2102-2106of flowchart 2100.

Flowchart 2100 will be revisited to further illustrate the presentinvention in view of the structural components in signal extractionmodule 2110.

In step 1706, spectrum isolation module 1726 isolates redundant spectrum1714 a-c from each other into separate channels, resulting in channels1718 a-c (shown in FIGS. 21B-21D). As such, channel 1718 a comprisesredundant spectrum 1714 a; channel 1718 b comprises redundant spectrum1714 b and jamming signal spectrum 1716; and channel 1718 c comprisesredundant spectrum 1714 c. Each channel 1718 a-c carries the necessaryamplitude, phase, and frequency information to reconstruct modulatingbaseband signal 308 because redundant spectrums 1714 a-c carry suchinformation. However, channel 1718 b also carries jamming signalspectrum 1716 that may prevent channel 1718 b from being used toreconstruct modulating baseband signal 308, depending on the relativesignal strength of jamming signal spectrum 1716. Step 1706 and channels1718 a-c were first discussed in FIGS. 17A and FIGS. 17E-G,respectively, and are re-illustrated here for convenience.

In step 2102, demodulators (or detectors) 2112 a-c demodulate redundantspectrums 1714 a-c (in channels 1718 a-c, respectively), resulting indemodulated baseband signals 2108 a-c, respectively. Demodulators 2112a-c are consistent with the type of modulation used to generateredundant spectrums 1714 a-c. As such, example embodiments ofdemodulators 2112 a-c include but are not limited to: AM demodulators,FM demodulators, and PM demodulators, and demodulators that candemodulate redundant spectrums that are combinations thereof.Furthermore, the present invention can be operated with other modulationschemes that are not listed above, as will be recognized by to thoseskilled in art(s) based on the discussion given herein. Furthermore, thenumber of demodulators 2112 need not be three, as is illustrated in FIG.21I. The number demodulators 2112 can be scaled to be consistent withthe number of redundant spectrums, or subset of redundant spectrumsreceived by (optional) medium interface module 1722, as would be wellknown to those skilled in the arts based on the discussion given herein.

In one embodiment, the down-converter 1516 is included in demodulators2112 a-c. In this case, down-conversion and demodulation are done in onestep so that isolated redundant spectrums are directly down-converted todemodulated baseband signals without using any IF stages. Directdown-conversion can done using the aliasing module 1902 that wassummarized in section 6.2.1.2.

In step 2104, error check modules 2114 a-c analyze demodulated basebandsignals 2108 a-c, respectively, to detect errors in demodulated basebandsignals 2108 a-c. In one embodiment, each error check module 2114generates an error flag 2109 whenever the corresponding demodulatedbaseband signal is determined to be erroneous. The error flags 2109 a-care sent with the demodulated baseband signal 2108 a-c to thearbitration module 2116. The arbitration module will use the error flagsto weed out erroneous demodulated baseband signals.

Error check modules 2114 a-c can implement any number of the possibleavailable error detection schemes to detect errors in step 2104.Furthermore, in some instances, methodologies can be used to correctdetected errors in digital signals. Some effective error detectionschemes that can be used for digital and analog signals will bediscussed below.

For demodulated baseband signals that are digital signals, error checkmodules 2114 a-c can implement cyclic redundancy check (CRC) or paritycheck to detect errors. A brief summary of which follows. CRC examines adigital bit stream and calculates an n-bit CRC character according to aspecific mathematical relationship. The CRC character is thentransmitted with the examined bit stream over the communications medium.The same calculation is performed at the receiver. If the receiver CRCcharacter agrees with that sent with the bit stream, then the bit streamis determined to be error free. IF there is disagreement, then an errorhas been introduced. Parity check also generates n-bit characterassociated with a bit stream; where the parity check character is basedon the number of logic “1”s or “0”s in the bit stream. The scope andspirit of the present invention includes all other errorchecking/correction schemes as will be understood by those skilled inthe art(s) based on the discussion given herein.

For demodulated baseband signals that are analog signals, error checkmodules 2114 a-c can monitor a pilot tone to detect errors. The pilottone is embedded in the redundant spectrums from which the demodulatedbaseband signals are generated. After calibration, any degradation inthe pilot tone may be evidence of signal interference.

In an alternate embodiment, error detection modules 2114 a-c cancomprise analog error detection module 2300 to detect errors in analogdemodulated baseband signals. Analog error detection module 2300comprises high pass filter 2302, and comparator 2304. Analog errordetection module 2300 operates as follows. High pass filter 2302 selectsthe out-of-band high frequency spectral components in the demodulatedbaseband signal 2108. These out-of-band spectral components are ideallysmall in amplitude. Comparator 2304 compares the amplitude of theseout-of band spectral components to some threshold level, and sets theerror flag 2109 if the threshold level is exceeded.

In alternate embodiment, arbitration module 2116 can detect errors inanalog demodulated baseband signals by examining the demodulatedbaseband signals to determine a consensus signal shape. Each demodulatedbaseband signal can then be compared with the consensus signal, whereany demodulated baseband signal that is substantially different from theconsensus signal is deemed erroneous. Implementation of this scheme ondemodulated baseband signals 2108 a-c (FIGS. 21E-21G) will result inbaseband signal 2108 b being deemed as erroneous. It should recalledthat exemplary de-modulated baseband signal 2108 b was demodulated fromspectrum 1714 b that was illustrated to be corrupted with a jammingsignal spectrum 1716.

In step 2106, arbitration module 2116 selects an error free demodulatedbaseband signal, resulting in demodulated baseband signal 1720, which issubstantially similar modulating baseband signal 308. In the exampleillustrated in FIGS. 21E-G, demodulated baseband signal 1720 can beeither one of demodulated baseband signals 2108 a or 2108 c.

In one embodiment, arbitration module 2116 uses error flags 2109generated by error detection modules 2114, and an elimination process toselect the error-free demodulated baseband signal. Example eliminationprocesses were described in section 6.2.3.1.1, in flowcharts 2200 (inFIG. 22A) and 2222 (in FIG. 22B), to which the reader is referred to forfurther description.

6.2.3.2 Other Embodiments

The embodiment for signal extraction described above is provided forpurposes of illustration. This embodiment is not intended to limit theinvention. Alternate embodiments, differing slightly or substantiallyfrom those described herein, will be apparent to those skilled in therelevant art(s) based on the teachings given herein. Such alternateembodiments fall within the scope and spirit of the present invention.

IV. Conclusion

Example embodiments of the methods, systems, and components of thepresent invention have been described herein. As noted elsewhere, theseexample embodiments have been described for illustrative purposes only,and are not limiting. Other embodiments are possible and are covered bythe invention. Such other embodiments include but are not limited tohardware, software, and software/hardware implementations of themethods, systems, and components of the invention. Such otherembodiments will be apparent to persons skilled in the relevant art(s)based on the teachings contained herein. Thus, the breadth and scope ofthe present invention should not be limited by any of theabove-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

What is claimed is:
 1. A method of generating a communications signalfor transmitting a first and a second baseband signal, comprising thesteps of: (1) receiving a first modulating baseband signal and a secondmodulating baseband signal wherein the first modulating baseband signaldiffers from the second modulating baseband signal; (2) modulating afirst oscillating signal having a frequency f₁ with said firstmodulating baseband signal to generate a first modulated signal; (3)modulating a second oscillating signal having a frequency f₂ with saidsecond modulating baseband signal to generate a second modulated signal;and (4) modulating said first modulated signal with said secondmodulated signal to generate a plurality of redundant spectrums, whereineach of said redundant spectrums contains information that isrepresentative of said first modulating baseband signal and said secondmodulating baseband signal.
 2. The method of claim 1, wherein step (2)includes the step of amplitude modulating said first oscillating signalwith said first modulating baseband signal, step (3) includes the stepof amplitude modulating said second oscillating signal with said secondmodulating baseband signal, and wherein step (4) includes the step ofangle modulating said first modulated signal with said second modulatedsignal.
 3. The method of claim 2, wherein step (4) includes the step ofphase modulating said first modulated signal with said second modulatedsignal.
 4. The method of claim 2, wherein step (4) includes the step offrequency modulating said first modulated signal with said secondmodulated signal.
 5. The method of claim 2, wherein each redundantspectrum includes amplitude, phase, and frequency information tosubstantially reconstruct said second modulating baseband signal, andwherein an amplitude of said redundant spectrums fluctuates in mass torepresent the first modulating baseband signal.
 6. A system forgenerating a communications signal that is representative of a firstmodulating baseband signal and a second modulating baseband signal,comprising: a first first-stage modulator configured to generate a firstmodulated signal using the first modulating baseband signal and a firstoscillating signal at a frequency f₁; a second first-stage modulatorconfigured to generate a second modulated signal using the secondmodulating baseband signal and a second oscillating signal at afrequency f₂ wherein the first modulating baseband signal differs fromthe second modulating baseband signal; and a second stage modulatorconfigured to modulate said first modulated signal with said secondmodulated signal to generate a plurality of redundant spectrums, eachredundant spectrum representative of said first modulating basebandsignal and said second modulating baseband signal.
 7. The system ofclaim 6, wherein said first first-stage modulator and said second firststage modulator are both amplitude modulators, and wherein said secondstage modulator is an angle modulator, wherein each redundant spectrumincludes amplitude, phase, and frequency information to substantiallyreconstruct said second modulating baseband signal, and wherein anamplitude of said redundant spectrums fluctuates in mass to representthe first modulating baseband signal.
 8. A system for generating acommunications signal that is representative of a first modulatingbaseband signal and a second modulating baseband signal, comprising: afirst amplitude modulator configured to generate a first amplitudemodulated signal using the first modulating baseband signal and a firstoscillating signal at a frequency f₁; a second amplitude modulatorconfigured to generate a second amplitude modulated signal using thesecond modulating baseband signal and a second oscillating signal at afrequency f₂; and an angle modulator configured to angle modulate saidfirst amplitude modulated signal with said second amplitude modulatedsignal to generate a plurality of redundant spectrums, each redundantspectrum representative of said first modulating baseband signal andsaid second modulating baseband signal.
 9. A method of generating acommunications signal for transmitting a first and a second basebandsignal, comprising the steps of: (1) receiving a first modulatingbaseband signal and a second modulating baseband signal; (2) amplitudemodulating a first oscillating signal having a frequency f₁ with saidfirst modulating baseband signal to generate a first modulated signal;(3) amplitude modulating a second oscillating signal having a frequencyf₂ with said second modulating baseband signal to generate a secondmodulated signal; and (4) angle modulating said first modulated signalwith said second modulated signal to generate a plurality of redundantspectrums, wherein each of said redundant spectrums contains informationthat is representative of said first modulating baseband signal and saidsecond modulating baseband signal.
 10. The method of claim 9, whereinstep (4) includes the step of phase modulating said first modulatedsignal with said second modulated signal.
 11. The method of claim 9,wherein step (4) includes the step of frequency modulating said firstmodulated signal with said second modulated signal.
 12. The method ofclaim 9, wherein each redundant spectrum includes amplitude, phase, andfrequency information to substantially reconstruct said secondmodulating baseband signal, and wherein an amplitude of said redundantspectrums fluctuates in mass to represent the first modulating basebandsignal.
 13. A system for generating a communications signal that isrepresentative of a first modulating baseband signal and a secondmodulating baseband signal, comprising: a first first-stage modulatorconfigured to generate a first modulated signal using the firstmodulating baseband signal and a first oscillating signal at a frequencyf₁; a second first-stage modulator configured to generate a secondmodulated signal using the second modulating baseband signal and asecond oscillating signal at a frequency f₂; and a second stagemodulator configured to modulate said first modulated signal with saidsecond modulated signal to generate a plurality of redundant spectrums,each redundant spectrum representative of said first modulating basebandsignal and said second modulating baseband signal; wherein said firstfirst-stage modulator and said second first stage modulator are bothamplitude modulators, and wherein said second stage modulator is anangle modulator, wherein each redundant spectrum includes amplitude,phase, and frequency information to substantially reconstruct saidsecond modulating baseband signal, and wherein an amplitude of saidredundant spectrums fluctuates in mass to represent the first modulatingbaseband signal.